eMarketer remarks on increased concerns about click fraud, pointing to SEMPO research showing 77 percent of search marketers are concerned that some unknown proportion of the clicks they win may be bogus. The figure kicked around by many experts and analysts, more of a gut guess really, has been between 10 and 20 percent of all clicks. One search firm executive, though, accused the major search giants in a blog post of turning a blind eye to the problem, not least because they wind up profiting from the fraudulent traffic as much as they do the real traffic.

BlowSearch's head of marketing wrote on his blog that both Google and Overture were fibbing when they said they had dedicated teams ferreting out click fraud.

He said that one piece of evidence of their lack of good faith was the fact that they did not reveal the click sources for bogus traffic that advertisers point out and for which they get credited. That means, he alleges, that clicks from those same sources get billed to other advertisers who haven't been paying attention quite as closely.