And the con-click rate is even higher for search engine ads:
Fake clicks on search engine PPC ads hit 28.2%, up, again more than a full point from Q3's 27.1%; down a hair, though, from 2007 Q4's 28.3%.
Botnets are driving a fair amount of the clicks: 31.4% of fraudulent PPC clicks come from bots, up from 27.6% in Q3, and way up from 2007's Q4 click fraud rate of 22%.
There's some indication that click farms are being cultivated again: paid clickers paid to click pay-per-click banners to pop the ad's numbers.
If your business buys PPC advertising, pay extra attention to click through rates. And be wary of them.
Click Forensics has a Click Fraud Index here.