PG I'm not defending google but there's a tremendous amount of fraud in this business. Any solution has to account for the fraud factor.

From my experience neither Yahoo or Google has the correct algorithms to prevent fraud. I know this because we have parked domains and I can tell when various parked domains get spidered and all the sudden we get a check in the mail for the revenue that bots must have created.

The reason google/yahoo don't do a better job is that the fraud clicks earn them money. But when they are alerted (by the advertiser) they come down hard and fast (as show by the OP)