I have pulled the ad from Ad Words just because it became not cost effective for me. I suspect because of the click fraud but my time is too valuable for me to try figure that one out and then try to proof something to Google.
Eventually it's their problem if my site (as probably other sites) are not making any profit on the their PPC. I have other source of revenue. They do not.
PS: The overture probably 10 times worse at detecting click fraud. Google does decent job comparing to overture.