Since you are using js for tracking, people can easily disable js and then your system fails. Try checking the log files and see how many people are visiting this http://example.com/product.php?WT.mc_id=campaignID page every day.
About the fraud clicker, do you mean that if they diable js, we can't see those visits/clicks in webtrends report but Adwords will still count those clicks and there will be a gap?
Yes since adsense has counted a click and your tracking system failed due to js disable.
Yet, if so, I think we can't do anything about it so far.
Yes you can do many things :).
[edited by: engine at 2:06 pm (utc) on July 4, 2006] [edit reason] examplified & de-linked [/edit]