Probably Forbes. The 4 are the Waltons, of WalMart fame. As for the others: Bill Gates, Paul Allen, Larry Ellison, Michael Dell, and Sheldon Adelson. Warren Buffet did get a degree, so actually of the top 10 (2006 list) it's 1 degree, 4 inherited, and 5 drop-outs. Buffett was already an entrepreneur with several revenue streams and felt college would be a waste of time, but he went because his father wanted him to.

And of course Steve Jobs dropped out (and started attending only the classes that piqued his interest), and Woz didn't get his degree until after Apple.