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John Zimmer

In 2006, John Zimmer took a job with Lehman Brothers in real estate finance. He felt no passion for the job and he left in 2008 to co-found Zimride, a ridesharing and carpooling business.

He remembers being castigated by a friend’s mother when he told her he was leaving the company to start his own business. “She said ‘How could you leave a sure thing like Lehman for a crazy idea like a rideshare company?’ Three or four months later they went bankrupt.”

Despite Lehman Brothers’ ignominious end, Zimmer still cites his time there as a valuable experience in building a new business. “Raising money and having a background in building financial models was helpful,” he told CNBC.com in an interview.