I haven't posted here before, but it seems like this has been overlooked enough that I should mention it.

"The deal will see Google pay Fox at least $900m (£472m), provided certain web traffic targets are met."

It makes absolutely no difference if MySpace becomes unpopular, because then Fox doesn't get paid. The only risk Google is taking is if people don't click the ads, but if they simply stop going, there's no problem.