Safe within the confines of Y Combinator, a kind of Mecca for geek entrepreneurs, Mark Zuckerberg spoke about the differences between 'The Social Network,' (aka the Facebook movie) and the real-life founding of his company. On the one hand, the film's costume design was dead on. But the rationale for Zuckerberg wanting to build Facebook (a girl)—not so much. Zuckerberg said the filmmakers "can't wrap their head around the idea that someone might build something because they like building things."