I turned down Facebook: Mark Zuckerbeg's college room-mate admits expensive mistake Mr Green, who remains friends with the Facebook founder, shared a dorm with him at Harvard in 2004. He was asked by Mr Zuckerberg to abandon university to start the social networking website. But Mr Green listened to his father and stayed at Harvard while his friend moved to Silicon Valley and begin his rise to becoming a billionaire. With Facebook expected to file for an initial public offering soon Mr Zuckerberg, 27, is now worth an estimated $17.5 billion (£11 billion). Mr Green said he had decided not to join Mr Zuckerberg in the Facebook venture after their previous project, Facemash, got them into trouble at Harvard. The rudimentary site was used to rate female students "hot or not." Mr Green told ABC News: "We'd got into a little bit of trouble with the previous project and my father, who's a professor, was not too happy with the prospect of me getting kicked out of school. Zuckerberg likes to make fun of my dad for this, but we're still very close. Mr Green went on to work for John Kerry's failed presidential bid but is himself highly successful. He now runs a multi-million dollar business called Causes, which aims to get people "civically engaged" by using Facebook to allow them to suggest charities and good causes to each other. Its aim is to "empower anyone with a good idea or passion for change to impact the world."