Internet Retailer: PPC advertising is big – and so is PPC click fraud

Clicklab, a firm that tries to divine whether or not a client's incoming clicks from ad campaigns are real prospects or fake clicks from fraudsters, reports that it finds up to half of clicks may be fraudulent. Sometimes publishers set up click farms in order to collect bounties for clicks in programs such as Google's AdSense. Other times, competitors are found to click on ads to deplete the competition's ad budgets. "Impression attacks" involve using bots to call up competitor ads and not click on them, making them seem less relevant to the constantly-evaluating algorithm that decides whether or not an ad gets placed in prime position.