Easily the best film I've seen this year. A lot of people will say how it defines a generation, or it's the film of the decade, etcetera, but I think what I liked most about it are the ways in which it isn't that. One of its themes (and it has several) is that innovation and invention don't always come from the need to make money. They just as easily come from more primal sources such as rejection and the humiliation of exclusivity. It's the same theme from Citizen Kane, which this movie apes a little, although it puts its rosebud moment at the very beginning of the film instead of the end.
Jesse Eisenberg is great as the creator of Facebook, and even though the character he plays (the real-life Mark Zuckerburg but he's really a character created by Aaron Sorkin) is pretty assholish (a fact pointed out to him in the first and last scenes of the movie) I had a lot of sympathy for him. And it's one of those great performances where the actor is able to empty himself of all of the charisma that probably got him the role in the first place.
I have mixed feelings about the writer Sorkin because I loved Sports Night and hated The West Wing, but I actually thought this was perfect material for him. Writing pithy political monologues for the fake president brought out his too-clever, too-precious side, but writing dialogue for narcissistic hyper-intelligent college students is a much better fit.