Google is apparently testing placing AdWords ads at the bottom of the search results, again. A WebmasterWorld thread has two people reporting seeing this recently.
I never noticed this before maybe it's not new. I see 3 Adwords Ads on top of the serps as usual and 3 at the bottom directly below the 10th result. There are no Ads at all to the right side of any keywords I check.
Saw this once today. I really wish they'd stop testing.
Whatever layout changes they're making impressions for the same spot are down 25% again today. This may explain that.
Forum discussion at WebmasterWorld.
Update: Here is a picture from @everfluxx:
Plus there are more pictures from readers in the comments below.