gregbo - 12:13 am on Feb 2, 2009 (gmt 0)

this is costing Google a lot of money.

If you stop to think about it, on top of the resources that are expended to process the clicks to charge for them, Google (and other engines) must apply various techniques to see if there are trends that match actual or presumed fraudulent behavior. For at least some of these clickstreams, they give refunds to advertisers. So at least some of the time, they expend resources in order to refund customers, that is, they spend money in order to lose money. Now it would not make sense for them to do this, unless they felt it was in their best interest to retain customers, who will in the long run make them profitable.