Microsoft's ex-CEO Steve Ballmer has become the ninth member of the $100-billion club with a net worth of $101 billion. Jeff Bezos is the richest of all with $212 billion wealth, followed by Elon Musk, Bernard Arnault, Bill Gates, and Mark Zuckerberg. The Facebook CEO is followed by Google Co-founders Larry Page and Sergey Brin, and Warren Buffett ranks eighth.