Fraudulent clicks accounted for 28.3 percent of all clicks on ad networks like Google's AdSense and the Yahoo Publisher Network during the fourth quarter of 2007. After some approximations, Freakonomics puts the number of publishers who are theoretically complicit in click fraud as high as 26 million. Which means advertisers need to get over it. Buy ads on a cost-per-action basis, where you only pay when clickers turn into buyers. Or do your own math and discount what you pay for a click accordingly — which is, in effect, what Google, Yahoo, and the like are already doing to publishers. Whining about the problem gives zero ROI. (Photo by Jason Upshaw)

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