He is deceiving the advertisers. They are paying for people interested in the ad, thats not what they are getting.
> The fact is that there is no tractable way for Google to separate people who are interested in supporting an ad-driven business from those who really are creating false ad traffic for financial gain.
Correct, but we can look at the average CTRs of other sites/blogs that focus on the same subject. That should give us a good understand of foul play (yes, of course there will be some false positives).