Okay, I'll play. Just for a goofy-ass comparison's sake, the
GI Joe sequel was delayed from a release this June until next March.
The rumored reason: Duke (Channing Tatum's character) died in the first ten minutes, which test audiences didn't like. He's become a bigger box office deal than the studio anticipated after
21 Jump Street (so they want to keep him around for the rest of the franchise). And they didn't want a "Channing Tatum the Soldier" movie to compete with "Channing Tatum the Male Stripper" movie.
So in other words: money. Studios will delay a movie and/or make changes if they think it'll sell more tickets, period. At least two of the posters here asserted definitevely that
Zero Dark Thirty was delayed for political reasons. I say that doesn't make any sense. It doesn't make Sony any money.
If the studio
did have a political agenda, I would think it would favor the incumbent administration to release this movie right before the election. Deservedly or not, killing bin Laden is considered a defense/foreign policy success for Obama. So unless 1) the movie makes the Obama team look stupid, which I haven't heard, or 2) Sony is a right-wing organization and doesn't want to remind the electorate of the "Obama got bin Laden" meme, which I also haven't heard, I'd say it's an unfounded assertion.