Even then, 500 servers? That's an incredible amount.

EDIT: Then again Facebook is using 60000 servers at the moment.

Facebook has a lot more than 100 times digg's registered users, though.

Not to mention a basically non-existent cachability profile, and an order of magnitude more functionality.

I'm assuming you mean Facebook has more functionality and no cachebility. That might be true but I wonder how expensive getting a Digg discussion(with 100-200 posts) page compared to say a 5 answer SO question or even just a simple Facebook profile.

As I understand it, a Facebook profile is anything but simple.