...who would be on it?<p>Specifically people who will help you on the product, NOT business, side of the startup: who've built great tech / proved to be exciting marketeers / done something new with social apps/community / will be awesome help in building something people want.
This is a purely fantasy question, right? In that case, off the top of my head: Peter Norvig, Fabrice Bellard, Bill Joy, Alan Kay, Chris Lattner (LLVM). These are just people who are my hacking idols and have a long history of actually getting extremely impressive stuff done.