Whitemark at Cre8asite Forums spotted Google testing a Google logo, in place of Ads by "Gooooooogle". It looks a bit like this:
Update: A DigitalPoint Forums thread has tons of examples.
Here is one with a small G logo:
And they were even spotted on DigitalPoint Forums itself:
People are upset that there blending work is not as blended with these new Google logos.
I don't believe I have ever seen this implementation, but I may have just missed it.
I think I like the text version better, either "Ads by Google" or "Ads by Gooooooogle."