I think it is no problem for Google to own almost any domain in the world. 520 domains is no big deal.
That's a large list. Looking through, though, I can't see how that's all their domains.. They'd have to have more than what's listed. The people who are saying google has 10k domains? That's more believable =]
Yep and many of those domains are set to redirect to main google page or another of google's main application pages.