Meet Twitter's billionaires

Current Twitter CEO Dick Costolo is credited with helping the company grow from its rocky adolescence into a company ready for a public market. Costolo joined the company in 2009 as COO after his media distribution venture Feedburner, was acquired by Google (GOOG). In 2010, Costolo became the company's new chief executive.

He's Twitter's fourth largest individual investor with a 1.6% stake. That is worth nearly $350 million at the opening price.

Costolo, who has a background in improv and teaches management classes at Twitter, helped the company turn tweets into profits by making mobile advertising integral to the company's money-making process. The company recently acquired mobile-focused ad exchange MoPub for a reported $300 million.

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