On 2/29/08 we reimbursed all advertiser accounts for all clicks from two publishers that signed up recently that have been sending fraudulent clicks throughout our ad network. If you log into your advertiser account and click on 'billing', if you change the 'date range' filter so you can see 2/29/08, you will see 'CLICK ADJUSTMENTS' there, with the amount that has been returned to your account. We apologize for this inconvenience. For any webmasters out there that are thinking about sending us fraudulent traffic. Do yourself a favor and save yourself some time and send your 'clicks' to another ad network that you can get away with that at.
That just tells where they (scammers) will be in 10 years. The short term gratification doesn't apply to the longterm.
all this is the most common problem that every ads network have to suffer... but sooner or later these fruads get detected and kicked out... beside now a days almost all ads network use special fraud click detection system.... so now its not really a major problem as there accounts will be suspended soon...