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."
Forum discussion at Cre8asite Forums & DigitalPoint Forums.

Comments:
webprofessor
12/11/2006 02:16 pm
I love the logo. It blends with all my ad's and I think it lends some credibility to the site's its displayed on.
Jonathan Mendez
12/11/2006 02:31 pm
There is no doubt this will increase CTR.
Gabs
12/11/2006 03:30 pm
Think of the bandwidth ;)
T. Blake
12/11/2006 04:03 pm
Google needs to be honest about their latest changes to Adwords and Adsense, helping those who are losing money or have gone broke. Although it does not apply to us we've read the reports. Revenue is way down, in some cases by 90 percent, for Adsense publishers. All the cute little logos do not matter to publishers affected by real economic issues.
Gabs
12/11/2006 05:39 pm
The last example is a classic.. Look at the 2nd ad... hehehhee.. Redirect anyone ?