I've noticed a trend tho. The dropouts that became successful were dropouts from Ivy League schools. Does that mean people from second tire schools should stay in school and finish their degree?
It undoubtedly helps. There're plenty of counterexamples though: Steve & Steve from Apple, for one. And I don't think it's more that they have a higher chance of starting a business, it's more that they have a higher chance of finding the money and time to succeed with their new business.
Also - the elephant in the room is plain old intelligence. Ivy League colleges tend to admit smart people, at least as closely as they can determine (there're always a few doofuses who sneak in, but they are a smaller proportion than at community colleges). Smart people have a higher chance of trying to start their own business, and a higher chance of being successful once they've tried.