>Even if we assume that Silicon Valley seed rounds only
  >account for 10 percent of angel investing in the US,

Surely they are way, way less than 10%. I mean tech is less than 10% of the US and the valley isn't the only place for angels. At 1%, which sounds more plausible, we are talking about controlling 50% of deals. That's not an innocuous number.

So, screw the 500,000 angels figure. Anyone with any actual knowledge want to tell us how much of the relevant market the top 10 angel firms control?