The Google Inside Adwords blog posts a link to a paper (pdf) that says that third-party auditing firms are misreporting click fraud, mainly in the form of fictitious clicks (which are reported as fraudulent, but are never recorded or charged as ad clicks by Google). They specifically name three firms - AdWatcher, ClickFacts, and Click Forensics - as exhibiting the "serious problems" of fictitious clicks. They also mention that they will "perhaps help third-party auditing firms improve their methods so that they can provide value to advertisers." Perhaps? Interesting word, there.