This is an amazing analysis done using the API of Angel List. The result: Silicon Valley is the epicentre of startup fundraising activity or Angel List focus on SV and many users list their primary locations as SV to be part of the community even if they live elsewhere….or a mix of both!
I don’t know whether AngelList data is skewed toward Silicon Valley investors or many investors list SV as a primary location even if they don’t live there but SV investors take large majority and they are very central. They are well-connected to pretty much every group and co-mingled with the second largest group, NYC/Boston investors(teal color).
Check out Making Sense of AngelList #1 : Investors.