I had my technology company in Austin, TX. Some were trying to convince us to relocate to Silicon Valley. It didn't take more than a day or two of research to realize what a bad idea this would have been. Frankly, it's amazing CA has been able to keep as many businesses as they have. DFA is just one of many companies seeking exodus from CA.
You need to understand a cluster. Industries cluster. The best, biggest cluster of tech companies (in the world) is in the San Jose area. Even the 'social networking' companies have simply moved to the nearest 'hip' urban centre (hence the Googlebus). This goes all the way back to Mr. Hewlett and Mr. Packard and their contract with the government to produce oscilloscopes (it's often a large government contract that starts the basis for this thing: hence the European aircraft industry (civilian) is centred in Toulouse, where the French government encouraged aircraft makers to relocate both before WW2 (to avoid German bombing) and post).
It might make more sense to start a hedge fund in Austin, Texas, but hedge funds are based in Connecticut (or Park Avenue, or Mayfair in London).
Medical device manufacturers (orthopaedics) cluster around southern Michigan/ Indiana, apparently.
Southern California has at least 3 clusters of which I am aware. The first is (obviously) the movie-creative industries (Pixar etc.) that centre around Hollywood. The second is the pornographic movie industry, which is based in the San Fernando Valley (and is a world leader in that market) but in structural decline. The third is a financial services cluster around the spin offs of Michael Milliken's office of Drexel Burnham Lambert in Beverly Hills (that went bust, but the people stayed and remained innovative in the fixed income field).
The 4th was the aerospace-defence cluster, (see the impressive factory scenes in the Roy Scheider/ Elmore Leonard '52 Pickup'). That started with WW2 and lasted until the end of the Cold War. There were literally hundreds of specialized components manufacturers. I think that is pretty much all gone, now.
Why this is so is an interesting debate but goes under the name 'external economies of scale'. The infrastructure and personnel are already there for new startups, ditto the service providers (lawyers, IT, landlords etc) and the business angels. This can offset a high cost of living and doing business.
You get tech companies in Texas (Ross Perot's EDS, Dell etc.) but they don't tend to be the bleeding edge ones (the other 2 clusters are the Triangle in North Carolina, and around Boston, where DEC was founded).
On the other hand, oil drilling technology is Houston, hands down, in the world. There's stuff in Aberdeen, Stavanger etc but Houston.