Richard Ball of Apogee Web Consulting dives a little deeper into the click fraud issue in this post on his blog. He talks about ways of minimizing click fraud in the Google and Yahoo! content networks, but interestingly, he points out that not all click fraud is coming from the content network.

It turns out that some of the content partners that Yahoo and Google distribute their PPC ads through are not considered "content" partners and are actually part of the search network. What does this mean? It means that some of these search partners have the same incentive (a revenue share on clicks) that content partners do - and with that incentive comes the temptation to drive fraudulent clicks.

Now I will say that becoming a search distribution partner is (and should be) a lot harder than joining the Yahoo! Publishers Network or Google AdSense - and you would think the search engines would guard the gates when it comes to search distribution partners since that is key to their core business. However, Yahoo! has proven that they are willing to work with potentially sketchy partners in the search network (as described in a sidebar of the print version of BusinessWeek). Also, if I understood correctly, Richard points out that the PPC ads on parked domains might actually be coming through the search network, and not the content network.

If this is true, and some of the search traffic advertisers are paying for falls into what most of us would consider a content page, the search engines are going to have some unhappy advertisers on their hands. When I place search ads, I want them to show up on search engines and search engines only.

So make sure you read Richard article and utilize his suggestions for minimizing content network click fraud. And next time you talk to someone from Google or Yahoo! see if you can get an explanation of why your search ads are showing up on sites that aren't search engines.