Just found this article: http://www.cbsnews.com/stories/2006/05/05/tech/main1590240.shtml Google are looking to settle with $90M. You have to have been doing something wrong to want to settle for that amount. Anyway one useful bit to gleen from the article is that the company estimated that 35% of its bill was click fraud. Probably not a bad figure to work into you calculations if youre going for some of the bigger terms. Notting
There should be 2 types of rates: Cost per click (very cheap) and Cost per target (i.e.: if you close a sale, people get through to a certain place of your web, see x amount of pages... -> much more costly)