whenever this topic comes up i always think of the people who never finished college. bill gates, jobs, eminem, etc. i don't think people like that are very rare

in the US it's not a big deal if you go to college or not. more important is whether you have ability

in one of pg's "creating a silicon valley elsewhere" essays he mentioned it may be more acceptable in the US for a PhD to start a startup than it would be in the UK. i think that sort of free-form climate is necessary for innovation

in fact those essays are pretty relevant here

http://www.paulgraham.com/siliconvalley.html

http://www.paulgraham.com/america.html