Qualifications
A PhD from a top engineering school helps (source). Actually, dropping out of a PhD program in computer science and/or another form of engineering from a top school helps.
The degree itself means little to nothing in Silicon Valley and to investors, but the fact that you were admitted to such a selective program is a big deal. And the program matters.
Stanford is perceived as highly entrepreneurially-oriented. In fact, the President of the University sits on the boards of Apple and Google—and his thesis when he was at Stanford was all about how useless PhDs are because the computing world changes so fast that it doesn't make any sense to try to get all "philosophy" on it. Nobody can predict anything—so just code. Build stuff. Let Adam Smith and the marketplace rule.
Stanford is the top dawg by a mile. Yes, Harvard and others have great, smart people. But they don't have the same cowboy culture of Stanford, which now has a long history of supplying brains to the Beast. Good luck gettin' in.