I did a quick search and did not see anything. I am getting a lot of image ads now that do not say "Ad by Google" I think they look better but was wondering where they are coming from and if its a new trend.
Why is it so random? Sometimes they have the arrows where you can scroll through the ads, and then you can do a page refresh and the function will be gone? I also think the Ads by Google should be taken off image ads at least, text ads it blends in more but adding text to the botom of the image should be taken away!! Anyways if we've solved the OP i was wondering if there is a firm conclusion on whether Image Ads pay less than Text Based Ads? Because i like image ads better, but do text-ads get more $ per click than a text ad?
I'm sure its "normal" what I was wondering is how it gets removed. I have an adwords account and there is no option for anything like "remove sponsor stamp". I know Volvo is running a big campaign now so my best guess is its on a per case basis for large advertisers running big campaigns.
I've seen them as well ... had to look a second time when the "Ads by Google" was not showing, thought someone had hacked my site.