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?
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.