Marc Andreessen at Opsware headquarters in Sunnyvale, 2003.
Paul Sakuma, Associated Press
He spoke for Hewlett-Packard's board when it showed ex-CEO Mark Hurd the door—and is now part of the team searching for Hurd's successor. He played a role in eBay's spinoff of Skype—buying a $50 million chunk in the process. And he has the ear of Facebook founder Mark Zuckerberg as that company marches toward battle with Google.