This article was interesting, it covers how much is lost in click fraud and such. http://www.businessweek.com/magazine/content/06_40/b4003001.htm?chan=search
I just got my BW in the mail today and the cover story about click fraud definitely caught my eye. Click fraud is ultimately costing consumers more for the products and services they desire because of increased marketing costs due directly to invalid clicks. The only ones profiting from the click fraud are Google, Yahoo and the unscrupulous individuals mass producing clicks on turnkey MFA sites.
Good article. Sometime needs to be done by Google and Yahoo to stop offshore clicks from charging US companies money.