If you quit a company, do a successful startup, and then get re-acquired by the company you quit in the first place, chances are that you don't want to go back to work for them again. If you did, why did you quit your job in the first place?
I wouldn't spit on it obviously, but considering some of these guys' former positions at Google, they had probably made a good amount from stocks and such. What I'm trying to say is that it's probably in the same order of magnitude of their worth before that.
Just a guess really, but what they are doing now make be considerably more exciting than what they were doing at Google previously.