http://www.paulgraham.com/siliconvalley.html
I live in Alabama. I joke that "high tech" here means "installing Windows and supporting Sharepoint" and it's not far from the truth. If I weren't the "trailing spouse" of an academic there's no way I'd live here given my skill set. It follows that people with similar or complementary skill sets to mine are hard to find here.
I have friends on the west coast who can pull together a project using friends and colleagues working in their spare time (gee, I wonder how Apple got started...). Similarly, when I was working in California I would frequently get requests from colleagues to contribute to their projects and often give them finished pieces they could plug into their projects the next morning. This kind of talent density is a huge "force multiplier". In the time it would take me to, say, find a designer or scalability guy I can work with who is willing to put sweat equity into a project, or do something for me for a few bucks, blah blah blah -- in Silicon Valley it would already be a working demo with seed money.
In fact, it's worse than that. I've been trying to find locals to work with me on stuff for years. I've built projects start-to-finish (but with missing pieces) several times over in that time.