gregbo - 11:49 pm on Jul 6, 2006 (gmt 0)

Also, it would be interesting to know how the cost of click fraud compares to the cost of waste circulation in other media. All advertising media have a certain amount of slop built in (direct mail that ends up in the wastebasket, TV commercials that go unwatched, newspaper ads that don't get read, etc.), so click fraud--annoying as it might be in principle--could be no more of a problem in real-money terms than impressions in other media that are paid for but not actually delivered.

But there is slop in online media -- ads that are clicked on but no conversions are made due to lack of interest; banners, videos, etc. that are ignored. Click fraud is an additional charge to the advertisers on top of slop.