VC investment is very power law, and SV dwarfs other places: http://www.citylab.com/work/2013/06/americas-top-metros-vent... , especially controlled for population.

See also pg's "Cities and Ambition" http://paulgraham.com/cities.html. People move to SV to do startups because everyone else moves to SV to do startups. The field of economic geography studies this phenomenon.