"Google Scale" is not really all that big of a problem as long as competent people are involved. Google's approach is to basically accept that everything is O(N) and simply through enough hardware at the problem that it's not an issue. RDBMS's often let you do things as O(log N) but they risk O(N^2) or even O(N^N) so your developers need to know what they are doing.

PS: The median developer at any large company is practically incompetent, so it's probably a vary good trade off once you have data centers of that size. However, for comparison Slashdot ran on 4 fairly cheap machines for a long time.