These two charts show the top 10 installers by number of installs in 2009 and 2011. A few interesting observations:
1) SolarCity, Real Goods Energy, Verengo and PetersenDean are clearly the winners in terms of growth and scale.
2) REC Solar interestingly dropped significantly from 2009 to 2011 with decreasing installation volume despite operating in a growing market.
3) Akeena went from # 4 in California in 2009 to exiting the business in 2010.
There were 400+ installers in the CSI data in 2011 that installed at least 1 system. The Top 5 installers in 2011 took roughly 1/3 of the entire residential solar market in California. A clear proof for the long-tail distribution of the installation market.