[giantrobot]

Silicon Valley has a confluence of things many other areas do not have.

1. Several high class feeder schools in the area including but not limited to Stanford and UC Berkeley. Note the feeder schools have robust CS programs but also renowned business and law schools.

2. A robust banking sector in San Francisco (for access to Old Money).

3. A bunch of New Money investors (Sand Hill Road gang etc) that you can wine and dine in-person.

4. California has a ton of high tech businesses besides just plucky Web startups.

A lot of supposed Silicon * regions have one or two of these things but rarely all within a two hour plane ride of each other (if not closer). Austin is nice and all but Silicon Valley (the nine-county Bay Area) is a megaregion with a population of over 7 million people with another two million in the combined statistical area. It's got twice the population of the San Antonio and Austin MSAs combined. That just makes for a much larger pool of we-don't-need-to-relocate employees for start ups or new efforts for existing companies.

It sucks Silicon Valley is so damned expensive but some other regions just being cheaper isn't going to pull away many startups. Despite bitching about taxes companies really like the fact non-competes are basically void in California. They incorporate and "headquarter" in tax havens anyways.