Although the majority of Lost has been well received, several different elements have received much criticism.
Nikki and Paulo were two of the most disliked characters on Lost.
Ana Lucia's death was planned from the beginning.
When Ana Lucia Cortez became a main character in Season 2, producers found many fans disliked the character. Her "tough girl" attitude turned many people off, along with her accidental killing of Shannon. The producers claimed that her character would "arc", which she did right before she was killed off in "Two for the Road". Long before the episode even aired, though, an insider claimed that the producers were fed up with Rodriguez's behavior, both on and off set and that she would be killed off, like Maggie Grace, who was also rumored to be difficult to work with.Lost producers denied rumors that she was killed off because of Ana Lucia's unpopularity or that Michelle Rodriguez was frustrating to work with. The main rumor seemed to be that Ana Lucia (as well as Libby) were killed off because the actors who played them, Rodriguez and Cynthia Watros, were arrested for drunk driving in December 2005. Rodriguez pleaded not guilty, and was sentenced to five days in jail. Michelle only served sixty-five hours of her jail sentence, before being let out due to jail over-crowding. Producers denied that Ana Lucia would be killed off because Rodriguez had a DUI and jail time even before she was killed off; they claim that Ana's death was planned when Rodriguez was cast, because Rodriguez had a "nomadic spirit" and didn't want to be on the show for more than a year. 
Michael's frequent screaming and obsession for his son was noteworthy and frequent enough for it to grate on the audience. A stretched out "Walt!" exclamation (spelled with numerous extra "a"s) was the center of numerous parodies and quickly became an internet meme.    
Nikki and Paulo have never been well liked.
Many fans have voiced their annoyance of the lack of information provided for the character, especially with the wasted opportunity when Cynthia Watros appeared as a Guest Star in "Meet Kevin Johnson".
Other In-Show Criticisms
Sayid in a flashback.
"I just wonder, going forward, if the flashbacks will begin to seem like crutches, somewhat repetitive fare that occupies much of the hour while the Island stories go forward verrrry slowly."-Maureen Ryan, critic 
After the first season, many viewers of the show began to grow tired of the flashbacks. They were perceived by some to be repetitive and recycling information we were already aware of; flashbacks have gotten less important than they were in the first season, taking away from the on-island storylines. The producers have found new ways to make flashbacks interesting, such as flashbacks of on-island incidents, both before and during the main protagonists time on the island and, from the end of season 3 onwards, flash forwards.
"There’s been a pervading sense that the creators really don’t know what the hell is going on, and that they’re just as surprised to find out what’s happening as the audience is."-Steven Simunic, critic 
Many complain that Lost moved too slowly and there is a lack of answers in the show. This has turned many people off, even Lost fans over time.  Typically, Season Two of Lost has been under fire the most for having little or no action in most episodes.   The season three premiere had twenty percent less viewers than the season two premiere, and many critics worried that the producers were just making it up as they went along.  Damon Lindelof was aware of this, saying in an interview, "There was unease that they were making an investment in a show that is complicated, without any sense of where it is going to lead them, Fans have been saying, 'Are you making it up as you go along?'"  However, many critics have been happier with Season 3, because they claim there's been more action and some things are getting resolved. 
Additionally, the announcement of a definitive end to the series has allowed the writers to reveal answers at a steady pace, as opposed to "stalling for time".
With all the mysteries that the writers have created during the course of the show, fans were expecting as many answers as possible to be given in the "The End". Instead of answering questions, the finale seemed to go a more emotional route. Some fans began to backlash for the fact that the writers 'dropped' the mysteries and failed to give a greater purpose to them.
Some viewers have complained about the flash-forwards which were a major part of the narrative in season 4, criticizing that they were spoiling (part of) the outcome of the "present day" on-island narrative. Anyone who was shown as alive in the flash-forwards (the Oceanic 6, Ben) couldn't die in the present day narrative, thus taking away part of the suspense for the season.
Some fans have expressed discontent with the DHARMA Initiative narrative in season 5. While DHARMA was given an anticipated close-hand portrayal, this focused on day-to-day trivialities. Despite the screen time afforded, greater questions of the mysterious organization as it was portrayed in seasons 2 and 3, were neglected. 
Some fans are dissatisfied by the (perceived) increasingly frequent number of continuity problems. This can be dates not matching up (such as Charlotte being given a 1979 birthdate in "Confirmed Dead", but then appearing as a young girl in 1974 in "LaFleur"), convoluted timelines (in episodes such as "Meet Kevin Johnson"    or "The Life and Death of Jeremy Bentham"   ) and details between a character's first-hand account of past events and a later episode that shows these events not matching up (Locke's encounters with the Oceanic 6 in "The Life and Death of Jeremy Bentham" versus what people said about those encounters in "There's No Place Like Home, Part 2" and "Because You Left", Danielle Rousseau's backstory as shown in "This Place Is Death" and "Dead Is Dead" versus her own account in "Solitary", "Numbers" and "Exodus, Part 1"). These fans, while not necessarily assuming that the producers and writers are "making it up on the fly", at least suggest that they fail to pay attention to a lot of details, especially since they have someone on their team whose job is specifically that.
In response to those complaints, executive producer Damon Lindelof has stated that "the boards can be really toxic" when it comes to continuity problems, defending himself that "it's television".  The problem with Charlotte's birth date has even led to a brief dispute between Lindelof and fellow executive producer Carlton Cuse and actress Rebecca Mader, who played Charlotte, after Lindelof and Cuse initially incorrectly blamed Mader for being responsible for the inconsistency. 
Women and minorities
While Lost has had one of the most diverse television casts in history, after the airing of "The Candidate" in which those in the main cast who died were all minority characters, some fans voiced skepticism at the treatment of women and minority characters on the show.
Prior to "The Candidate" the most notable occurrence of criticism for treatment of racial issues happened when Harold Perrineau, who played Michael Dawson, stated that the show's treatment of black characters was potentially problematic:
Listen, if I'm being really candid, there are all these questions about how they respond to black people on the show. Sayid gets to meet Nadia again, and Desmond and Penny hook up again, but a little black boy and his father hooking up, that wasn't interesting? Instead, Walt just winds up being another fatherless child. It plays into a really big, weird stereotype and, being a black person myself, that wasn't so interesting. -- TV Guide
He later emphasized that he was not directly accusing the show of racism, but relating his personal experiences:
It’s just an observation. Michael’s a black character and I’m a black person, so I have feelings based on it. I can’t really separate those two things — my race and my country and all that stuff...I accept that this is what [the producers] need to happen for something else to happen later...I recognize that when you make a racial comment it polarizes people. That was never the intention. It’s like, “No, no, no, don’t choose sides. I’m just telling you this is what I think. Everybody stay on whatever side you’re on; this is my point-of-view.” -- Entertainment Weekly
After the airing of "The Candidate", some fans expressed disappointment at what they perceived as the mishandled character development for minority characters. "They killed off four main characters in one fell swoop; three of those characters had been with us since the very first episode, and all three of those original characters were also people of color...LOST was initially a pretty sly, clever commentary on post-9/11 America. All that’s gone by the wayside," wrote Cara Kulwicki and Lauren Bruce of Feministe. S.E. Smith of This Ain't Livin' noted: "...Lost is a show where people die. No, that is not new. Yes, the show has a habit of coming up with weird death scenes. Yet, this was, well, it was blatant. They killed the three most obviously nonwhite characters."
Cuse and Lindelof have "maintained radio silence" since the end of shooting for the series finale, and have not made any official remarks regarding the subject or any other topic related to the show.
10 p.m. Timeslot (US Only)
Season Three of Lost struggled to gain viewers because of timeslot and scheduling problems.
"We literally saw a doubling between ['Lost' airing in] the 9 and 10 p.m. slot in TiVo-ing, more than double actually, I think that's a factor of it being on at 10; more people are DVR-ing it."-Stephen McPherson, ABC President 
Between the hiatus in Season 3 from "I Do" to "Not in Portland", ABC announced that it would move Lost from its usual 9 p.m. timeslot to a 10 p.m. timeslot in order to avoid a ratings battle from American Idol and Criminal Minds.  That was the third timeslot move that Lost had undergone in three years.  Many people were sceptical of this move, including Lost actor Naveen Andrews. In an interview, Andrews was quoted as saying, "I think they should make it sort of like what it was before, I liked it when it started a little bit earlier, because a lot of the audience are kids, aren't they?"  Reports claim that Stephen McPherson, ABC Entertainment president, claimed that he wants to move Lost to either an 8 or 9 p.m. timeslot. When McPherson was asked what timeslot he'd think would be ideal, he joked that it should be "Saturday morning, 7.30." 
Season One and Two Scheduling
During the first two seasons, there was criticism from some fans due to the amount of repeats broadcast between brand new episodes. To appease fans, the schedule was changed for Season 3, to reduce the amount of repeats.
Season Three Scheduling
"ABC's "Lost" has lost nearly half its live audience - more than 10 million people - from the days it was a sensation."-CNN.com 
In an effort to help Lost's ratings, in the 2006-07 television season, ABC aired six straight Lost episodes in a row in October and November 2006, then went on a thirteen week break, before coming back with sixteen straight episodes. Lost came back in February of 2007, only to find that many fans had left after the long wait.  Shows like "Heroes" and "Jericho" suffered similar problems.  By the end of the 2006-07 television season, Lost finished 17th in the series programming results.  Due to the criticisms of the hiatus, and to once again appease the fans, the shows producers and ABC changed the scheduling again, announcing a new format for the final three seasons of Lost.
Season Four, Five and Six Scheduling
Some people have complained about the new format of the next three seasons to come, which will air from February to May of each year for consecutive weeks, without repeats. ABC and the shows creators have been criticised for spreading 2 seasons worth of content (48 episodes) across three seasons. The shows creators have stated that having 16 episodes per season allows them to pace the show as they need to in order to tell their story.
The WGA strike affected the fourth season, resulting in the planned sixteen-episode season being cut short. Instead, the fourth season had thirteen episodes broken into 8 episodes, followed by a break, then 6 showing beginning April 2008. The season finale was a special two-hour episode, but is usually referred to as a single episode. The episodes that were lost to the strike were instead produced for seasons five and six, as the production was contracted to provide a specific number of episodes, not seasons.
Season 5 has seventeen episodes. The first two episodes, along with a special recap episode aired on Wednesday January 21st, 2009. The remaining episodes aired on consecutive weeks with two other clip shows inserted on Wednesdays at the 8pm timeslot.
The show's last season, Season 6 also had eighteen episodes, which aired February-May 2010.
Other Outside the Show Criticisms
Sky One and Virgin Media (UK Only)
"Barring a last-minute deal, Virgin's 3.3 million subscribers will not be able to watch Lost, The Simpsons, 24 and other popular shows."-James Robinson, media correspondent 
For a while, BSkyB, the operators of Sky subscription based satellite television service as well as Sky One, UK broadcasters of Lost and Virgin Media, the major UK subscription based cable operator, had been debating their contract for carriage several of BSkyB's channels on the Virgin platform. Virgin Media claimed that BSkyB wanted to double the price of carrying Sky's basic channels package, which include Sky One, and BSkyB claimed that Virgin Media was trying to rip them off.  On March 1, 2007, Sky One was amongst several BSkyB channels dropped by Virgin Media, because of their inability to reach a new deal.  This meant that fans who wanted to watch Lost, along with other Sky shows, had to subscribe to Sky.  Both TV providers launched advertising campaigns against one another and talks have yet to resume.  Sky One is rumored to have paid £1 million an episode for the rights to air Lost in Britain. . Virgin Media have since purchased on-demand rights for Lost, allowing them to show episodes of Lost after Sky One has completed its broadcasts of the series. On November 4th a deal was signed for the channels to appear on Virgin Media, meaning that Lost is once again available to it's costumers.
- ↑ 1.0 1.1 USA Today: She shot Shannon; what's Ana Lucia's next target? William Keck; 11/15/2005
- ↑ 2.0 2.1 Actress sheds a tear over Lost Colin Mahan; 05/11/2006
- ↑ NineMSN: Sexy Rodriguez told to get Lost Snapper Media; 02/02/2006
- ↑ 4.0 4.1 Why Did Lost Kill Ana Lucia? Lindelof/Cuse Tell All! Michael Ausiello; 05/04/2006
- ↑ MSNBC: Michelle Rodriguez Released From Jail Early Associated Press; 05/30/2006
- ↑ Ana Lucia safe on Lost Colin Mahan; 02/14/2006
- ↑ BuddyTV: What Are They Up To? Lost's Michelle Rodriguez Kris De Leon; 05/29/2007
- ↑ Fox News: Sex, Bloodshed and Betrayal Served Up on 'Lost' Associated Press; 05/04/2006