David Sacks is a paradox. The entrepreneur and venture capitalist helped lay the foundations of the digital world we now live in: He was one of the members of what's known as the PayPal Mafia, alongside people like Peter Thiel, Elon Musk and Max Levchin. He’s also been an early investor in some companies you may have heard of: Airbnb, Facebook, Slack, SpaceX, Twitter, Uber.