Meshach writes "There is an interesting story at CBC which claims that Google loses one billion dollars per year to fraudulent ad clicks. The article contains an interesting description how how the company determines if a click is false. 'The company explained that it determines which clicks are invalid through a three-stage system. Most of the illegitimate clicks are automatically detected analyzed and filtered out in the first stage ... The second part uses automatic and manual analysis of the AdSense network to weed out false clicks before they are logged to an advertiser's account.'"