The future of PPC search ads - a move to Cost per action?

In this Wired article, author Charles C. Mann investigates the potential rise of cost-per-action search engines ad systems, in response to click fraud problems on pay-per-click systems such as on Google and Overture. One such CPA search engine already exists - Snap.com.

Although these CPA advertising models have been talked about for quite some time, there is disagreement in the internet and advertising industries about whether these ad systems will ever really take off and become the dominant payment model. Currently Snap.com has just 2% of Google’s advertiser volumes, and its website user numbers are probably even further behind that (making it hard to attract more advertisers, despite the effective payment model). Time, as the saying goes, will be the judge.