Forum Moderators: open
I feel that it has to do with their partners. Although they mention some key names they also take other partners who use spam sites that have the keyword in the names which give them higher rankings.
Since they make money when your URL is clicked... I think it gives incentive to people to be unscrupulous.
For ourselves we have talked to Overture about this but they deny fruad clicks exist (yah right why should they care...more money for them) We know it exists because of the ROI and again we haven't added or made any changes. Just more money out but not the incremental increase. We even lowered all our keywords over a few days. At first the money per day went down but then shot up to where it was before... now isn't that interesting?
Just my opinion