Sergey Brin

Net worth: $12 billion
Age: 35

Google co-founder continues to dominate search business despite facing strong headwinds. Company’s stock is down 30% in the past 12 months, slicing $6.7 billion from personal balance sheet. Posted better than expected earnings in January; trimmed staff and employee perks. Professor’s son emigrated from Russia, met partner Larry Page in a computer science Ph.D. program at Stanford University. Duo dropped out in 1998 to start Google from a friend’s garage. Sales: $21.8 billion. Net margins: 19%.