7. Jack Dorsey
Company: CEO and Cofounder, Square, Inc.
Jack Dorsey dropped out of college and cofounded hugely popular social network: Twitter. Together with Evan Williams, Biz Stone, and Noah Glass, he launched Twitter in 2006. He gets most of his fortunes from his roughly 4 per cent stake in the company. Dorsey stepped down as Twitter CEO in 2008 and is now its chairman. His main focus today is on Square, his mobile payments app that helped turn smartphones into credit card processing machines.