Found a great article.
Click Fraud Hits 14.8% For 1Q 2007: Click Forensics
"Click fraud is one of the reasons we try to wean our clients off of the pay-per-click model" . . . Read more
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Me too I want out !
Click fraud is part of the cost of advertising but there are ways to deal with a lot of it. It takes some work. There are several articles on the subject if you search Google using the link below:
http://www.google.com/search?hl=en&q=eliminating+click+f raud
I found this two very interesting articles with this search but there are many more:
http://www.bruceclay.com/articles/eliminateclickfraud.htm
http://www.clicktracks.com/insidetrack/articles/click_fraud_ how-to_1.php
The best advice I can give you is to monitor for it regularly, make adjustments when you see it and don`t use a PPC service without checking them out first.
If you get out totally, you may not be see at all...