Interesting,
yep the anti spam on mosts cpc engines are weak, hwever when I have requested data regarding our ad campaigns on adwords, its not been as in depth as I would have liked.
The click detective is a good idea, however they will need to have, or develop better anti spam than the engines have in place already. This is possible, as have written anti spam filters which have nearly matched those which remain secret on the the cpc engines I have used to generate revenue, this is done to validate the revenues being paid by the cpc engine to us.
I think google lean more towards conversion and actual sales when looking at the effectiveness of a link.
D