“The first, second, third company I went to work for, somehow I screwed them all up. Doing startups is all about making mistakes,” Biz Stone nervously admitted onstage at the New Context Conference in San Francisco. He'd just confessed that he didn't prepare anything so will talk about his biggest screw-ups, including one that could earn him many millions of dollars when Twitter IPOs. “Making mistakes for fun and profit,” the Twitter co-founder joked.