Zuckerberg's motivation, far from being driven by feelings of social inadequacy, was quite intellectual. He didn't know what would happen but he proved surprisingly adept at managing its growth. He resisted bombarding users with advertising, believing it best to let the service reach its natural market size without offending them. This is accurately portrayed in the movie; his early business partner Eduardo Saverin insists the company has to immediately "monetize" and Zuckerberg refuses. He still believes that growth is more important than short-term monetization. Since he has total control of the company, his opinion is the only one that matters. He is patently unimpressed with 500 million users. He looks instead at a planet approaching seven billion people and asks why they can’t all use Facebook. Harking back to those convictions he refined in the summer of 2003, he sees himself building the most efficient tool in history for sharing and communication between people. For him, Facebook is a tool for the empowerment of individuals which will make the world a better place. You'd never know that from the movie, but that's Hollywood.