I know it'd be impossible to know these stats, but it'd be interesting to see how many (recent) ex-Googlers went on to start their own successful startup. With that, it'd also be quite interesting to speculate how many of these business ideas could have benefited by being "within" Google.
In many ways it's a shame, although I think most of us can appreciate that the Google of yesterday is a different beast to the Google of today. One area where I think it could really hurt Google is in recruitment. I imagine the "20% rule" would have been a huge factor in getting the best engineers to work at Google. With this news, I can see some of the magic of Google disappearing in my mind.