do you have an affiliate program, could be an affiliate of yours doing some ppc.
you said nothing was being billed, billing has some delay built into it, are you sure no clicks are showing within the adwords account as well as no billing happening?
evil thought... MFA (made for adsense) sites were cleaned out a while back... but, is it possible today that instead of someone bidding some cheap keywords to go to their own site to solely make money off of their adsense ads, that they'd bid cheap for traffic on a site where their own adsense ad are known to be?
policing abusive affiliates, and other weird circumstances that do occur, makes me wonder why G would allow any party anywhere to run ads for and deliver paid traffic to a site they don't own. a permissioning system is sorely needed.
[edited by: superclown2 at 10:44 am (utc) on Mar. 25, 2009]
Interesting idea, but would it work? If they bid a low price their ad probably wouldn't appear, and even if it was high, out of nine ads on the page a visitor would probably click on someone else's ad anyway. I wouldn't have thought that it was economically viable but then some folks make money in Byzantine ways.
Of course, adwords listings often don't show all the time so it's possible not to show there but for there to be a campaign running.
the doubleclick referrers is more google traffic.
search for the referral url using the Google "link:" operator, may have to use "-site:" operator to clear out some things, to try and find where these links are... just a minor thought...
search operator help:
[google.com...]
So, do I just let sleeping dogs lie, and continue getting the benefit of someone else paying for my clicks? Or is there a possible downside to this? I'd be grateful for any comments.
You have my full attention. How can it do that?