If this kind of thing had happened on the front of tabloid papers or on random blogs or even if he were mocked on South Park or something, it would be something to shrug off. But this film is on its way to the Oscars and more than that it's the front runner for winning Best Picture (which is just bizarre to me. Inception and Toy Story 3 were both vastly superior imho). So here you have a film about your life that portrays you as a major asshole, backed by Hollywood heavyweights, watched by millions and millions of people around the globe, and has a good chance of becoming the Best Picture of the year and being cemented in cinematic history. That is not something even someone richer and more famous than Zuckerberg would be able to shrug off.
My cousin works at Facebook, I'm gonna ask her if anyone at work is talking about the movie or if it's totally not something they're discussing over there.