The world's youngest billionaire is now 26-year-old Dustin Moskovitz, who is 8 days younger than his former Harvard roommate and Facebook cofounder Mark Zuckerberg. The social-networking site's first chief technology officer, Moskovitz left in 2008 and started Asana, a software company that allows individuals and small companies to better collaborate. The company has attracted several of the same early backers as Facebook and may one day be worth something. For now, though, Forbes estimates Moskovitz's entire $1.4 billion fortune comes from his 6% stake in Facebook.