I'm wondering if Faraday's whole "the future can't change" shtick is for real.
I've always wondered about that statement as well, going back to the show about Desmond's constant from last season.
Desmond meets Faraday in the past at Oxford, and sees him transfer Eloise's (the rat) consciousness to the future where Faraday evidently trains it to run the maze. This is demonstrated when Eloise successfully runs the maze. Desmond blacks out and returns to the freighter. Then Desmond returns to Faraday's office (and I get the impression that he was only blacked out for a few minutes, maybe an hour) and discovers that Eloise is dead. Which means Faraday never actually had the chance to train her and so the FUTURE HAS BEEN CHANGED!!!
Time travel stories almost always fall apart under any scrutiny, so I hope the LOST creators are very careful and don't try to make the whole focus of the show about time travel.