Yoshikazu Tanaka

Tanaka presides over a world of opal-eyed digital zombies and pirates. GREE, the mobile social-gaming company he founded in his apartment in 2004, has become Japan's biggest social network -- of any kind. Globally it reportedly has 190 million users and expects to generate $2.5 billion in revenue this year. To gain a foothold in the West, GREE acquired U.S. mobile-game maker OpenFeint last year. The company's success has turned the boyish Tanaka into Asia's youngest self-made billionaire. Tanaka says he grew up obsessively playing NES games into the twilight hours. His parents thought he was wasting his time, he says. Clearly they were wrong. --Matt Vella