Nice piece, I had a bit of a problem with my sitemap from one site which was 301 to another site.
I showed a bag load of errors as the pages could not be found on the site, and Google are suggesting I edit my sitemap to permananely point the files to my new site.
In reply to Angela's statement about the Google refunds, their invalid click filters are not that good, and a click farm as you describe above will probably fool the filter as they look like real users browsing your site.
It is my experience that people working on click farms are given intrusctions to click on links on the site to simulate a real user experience in an effort to fool the search engine.
What is more, why would they do it if they were not generating an income?
An excellent post exposing another click fraud scam.
Lesliek1 Agree with Neil - the only surefire way to ensure that you get what you pay for is to audit your PPC campaigns with a third party provider. Of course engines will claim they are catching it (especially the 600 lb. Gorilla) - but in the end, do you really want the thief who robbed your bank today to become your security guard tomorrow?