4. Dustin Moskovitz
Worth: 2.7 billion
Background Info: Dustin Moskovitz, Mark Zuckerberg's Harvard roommate and Facebook's third employee, dropped out of Harvard and moved to California to work for the social-networking firm full-time. He was the first CTO and then became vice president of engineering. He left a few years later to start Asana, a software company that allows individuals and small companies to better collaborate. Reportedly sold around a 1% stake in Facebook last year but held onto an estimated 5% in the company, whose value has soared to $50 billion, based on the recent Goldman Sachs transaction.