8. Sean Parker
Worth: 1.6 billion
Background Info: Former Facebook president debuts as a billionaire based on the value the social networking site. His share: just under 3%. At 19, the serial entrepreneur co-founded Napster in 1999, the music sharing service that brought free music to the masses. The disruptive technology helped trigger the record industry's precipitous decline. Parker joined Facebook in 2004. Recently made more famous after being played by Justin Timberlake in the Oscar-winning film "The Social Network."