In terms of whether a concentration of talent in your area is desirable (e.g. more likely to find other talented people to do something that requires more than just your talent), undesirable (e.g. more competition, higher cost of living), or neutral, it depends on what your talent is and what you are trying to do with it.
California does have one feature that long predates the computer industry, but may have helped produce the “startup culture” in the computer industry, and currently serves as an attractor for talented employees. That is a law which makes almost all employee non-competition agreements clearly unenforceable.
http://www.bloomberg.com/news/articles/2015-03-17/silicon-valley-is-the-world-s-innovation-capital-because-of-a-technicality
https://techcrunch.com/2016/02/18/silicon-valley-keeps-winning-because-non-competes-limit-innovation/
http://fortune.com/2015/07/01/noncompete-agreements/