I think it is more important to note that the white, upper-middle-class denizens of the valley actually like (or ar least don't mind) being near people who are

I think it is more important to note that the white, upper-middle-class denizens of the valley actually like (or ar least don't mind) being near people who are not like them, relative to the other upper-middle-class people elsewhere. New York has some of that going too, but it's worth pointing out that the culture in New York subsumes you. New York could still become a tech spot, if it could overcome other difficulties, like the whole employer-owns-all-your-work default.