Paying only for ads that actually hit their mark has long been a goal of advertisers in any medium, but some marketers have opted to focus on cost-per-action (CPA) ads over cost-per-click (CPC) because of a perception that the former is less susceptible to fraud. However, a new report casts doubt on that perception.

The report comes from Harvard assistant professor Benjamin Edelman, who found that most buyers lack the technical know-how and resources to accurately track instances of fraud even in the CPA

"Enforcement requires fact-intensive technical investigation -- examining HTML code and packet logs to uncover infractions," Edelman said in his report. "The required skills have little overlap with the relationship-building and communication that otherwise drive affiliate marketing."

But despite his criticism of CPA advertising, Edelman pointed out that increasing technical resources would likely help advertisers detect and police fraud.