However, the researcher's own recent experiments don't always gel with Click Forensics' observations.

Edelman said that a system he has employed to monitor click-fraud activity on advertising networks by attempting to carry out the behavior has been able to scam just about every popular system, including that controlled by Yahoo's Omniture group.

However, the "robot PC" he created to carry out the click fraud wasn't able to create false impressions on Google's AdWords, which impressed the Web economics expert.

"The core problem is that it is still hard to determine whether the supposed clicks occurred, the search engines will always dispute published figures, and advertisers will be left uncertain who to believe," Edelman said. "In my own work using the robot, I've observed click fraud through almost every network, but not AdWords, not that it means it doesn't happen."

One of the problems in figuring out to what extent click fraud is influencing ad traffic is that neither the search networks nor their advertisers are particularly open with the data they retain about user behavior, he said.

People submit complaints to the search companies on an individual basis, but little comes of the reports other than automated responses, according to Edelman.

One approach that could help address the issue would be if companies like Google and Yahoo created message boards where advertisers could compare notes and draw conclusions about their shared experiences, the researcher contends.

Just as Apple has allowed its customers to vent about product problems in its public forums, the search networks could prove their diligence in fighting click fraud if they allowed customers to share information in public, the expert suggested.

"A different way to run the traffic auditing and review process would be to add this transparency, to allow crowds of advertisers to expose their problems and share complaints, that would allow much less leeway for the search providers to bury their results," said Edelman. "It's clear why they might not want to do that, but they could do it if they were really confident that there's no problem to be exposed."

Faced with the proposition, Google representatives said that the company would consider such an idea, but indicated that for now, it harbors no plans to introduce such a program.

"Without that type of transparency, the extent of the click-fraud problem will remain tough to nail down," Edelman said.