Nowadays there is a lot less click-fraud around than it used to be, specially with Google.
But that doesn’t mean it’s nonexistent. If you want to educate yourself on the subject, read How To Detect and Protect PPC Click Fraud and Make More Money From PPC Marketing.
According to ClickForensics, the industry average in PPC ads is: a 12.7% click-fraud rate. That means out of 100 clicks, almost 13 are click-fraud tricks. This is NOT the Google data, but PPC data, Google is a lot better than the average, but it still makes a point: lots of wasted clicks.
