The Social Network

If further proof was needed that Jesse Eisenberg is an infinitely more interesting and versatile actor than Michael Cera (to whom he is often - unfairly - compared), then just try to imagine the latter playing Mark Zuckerberg. No? Didn't think so. As previously shown in The Squid and the Whale, Eisenberg can summon an unpleasantly abrasive edge to his characters (the audience practically cheers when the long-suffering mother finally slaps him in that film) Likewise, his Zuckerberg makes no play for sympathy. Anything that we do feel for him is very hard won indeed - and usually short-lived.
The opening exchange perfectly sums him up: an obviously intelligent man with non-existent social empathy, even for his (soon-to-be-ex) girlfriend. She is merely the first in a stream of people driven to exasperation by his behaviour. It's rare when one feels sorry for movie lawyers but Zuckerberg's in the deposition scenes comes close, as his client's interventions do nothing to help his case. This is a man who insults his ex online and can't understand why she refuses to talk to him; who thinks nothing of discarding his only real friend in favour of the surface flash and ambition of Sean Parker, a man he regards as a soulmate because both were driven to invent in order to impress a girl (though tellingly Parker clearly couldn't care less about this early love whereas Zuckerberg never quite gets over Erica).
Motivations are left opaque but there are interesting suggestions. Saverin and Zuckerberg are both outsiders, looking longly at the exclusive clubs and the girls the members attract, and yet Zuckerberg appears to harbour a festering jealousy when his friend is accepted into one of the clubs (you could never describe Zuckerberg as a supportive friend; his main aim seems to be to undermine Saverin's confidence). Zuckerberg also wants some form of revenge on Erica but also seems to want her back, and equally important (baring in mind her apparent admiration for the rowing crews) he has a powerful determination to best the Harvard elite who shut out the likes of him. There's actually much fun to be had with the representatives of this elite, the Winklevoss twins. Their attitude about the honour of Harvard gentlemen might be gently mocked but they are mostly portrayed as sympathetically naive.
At the film's heart though is the destruction of the friendship between Zuckerberg and Saverin. It's far easier to warm to Saverin, who's endearingly gauche, and never once suspects that Zuckerberg and Parker are plotting to remove him from the company he founded. Even during the deposition scenes he seems hurt more than angry (his one explosion in Facebook's office involves him disconnecting Zuckerberg from the digital bubble in which he exists) yet the minute changes in his facial expression suggest that Zuckerberg feels the loss too. The break though is irreparable. If this all sounds terribly serious, it's not. David Fincher makes it a thoroughly enjoyable experience (and for CSI afficionados there's a "that's Hodges!" moment), with zinging dialogue, classy performances and a surprising emotional kick. Erica tells Zuckerberg at the beginning that it's not because he's a nerd that women won't like him, but because he's an asshole, and while the film mostly substantiates this view, our final image of the young billionaire is of him isolated at a computer, constantly refreshing Erica's Facebook page in the hope she'll accept him as a "friend", more a pathetic figure than anything else.