I think the key is though - and certainly the point I was trying to make at the start of the thread - it's not just ethnic diversity, though that's important. It's diversity of opinion and other cultural factors. There's an open-mindedness to Silicon Valley that is definitely not there in Houston - my in-laws are from Houston and I lived there for three years, and I don't think anyone would make the case that it's comparable to the Bay Area for that.

Yet that cultural tolerance has been shown time and again to be critical in attracting the creative class professionals which make Silicon Valley tick.

I'd agree that it's cultural tolerance that is the important factor, but I don't know if that results from diversity - I think it results from education.