Fountain of Youth: The Under 30 Hall of Fame
Mark Cuban, Dallas Mavericks
Cuban, an outspoken Texan, sold his software company Microsolutions to Compuserve for $6 million in 1990, and sold Broadcast.com to Yahoo five years later for $5.9 billion in stock. Today, he's best known for heckling the refs at Dallas Mavericks games, where he sits in the owner's chair. His latest venture is HDNet, a high-definition TV network.