Having so much success though can also mean that you don't have as much drive to make a great product because you're already set. Not that it must be the case here, but passion is hard to maintain when it doesn't really have much effect on your life.
Also, if the site can be run completely independently (and it looks like operational costs are rather low) then why even take VC in the first place? Surely the effects of hundreds of millions requiring a return could easily be predicted as eventually causing problems?