Even physical micro-hubs like coworking spaces where I live in Phoenix do not capture the serendipity of interaction that Silicon Valley provides.

Here you have to consciously decide to go where other startups are at. In Silicon Valley I just get a cup of coffee and there's a conversation at the table next to me about startups.

Although, I have to say Twitter enabled more fluid communication in the startup scene here. Enough to where I have been able to spot a couple people not at the typical hotspots.