Benjamin Edelman, the Harvard 'Spyware' Professor well-known for his analysis of the brokering of sub-premium online ad space, claims that up to 34% of ad messages sold through Yahoo's Right Media may be deceptive or "bad" advertising.

Right Media is the largest online ad space market for unsold inventory. It was acquired by Yahoo in 2007. Its clients typically sell their most desirable real estate at on ad networks where they can fetch premium prices, then vend the rest on Right Media, leaving the latter with comparatively less desirable ad inventory.

Since few legitimate labels are willing to buy second-class ad space, they're often filled with "bottom-feeders whose ads have a tendency to deceive," says Edelman (via BizReport), who took the liberty of listing the ads, which range from the type that promise free items ("Free iPhone!") without informing consumers of certain predicating obligations, to ads that look like operating system dialog boxes. There are also the infamous  "You have won!" ads, which fall short of the FTC's requirement that ads make their commercial nature evident.

Yahoo has denied any wrongdoing; meanwhile, Right Media released a statement saying it is deeply committed to providing advertisers, agencies, networks and publishers with a high-quality experience.

It also maintains that its Media Guard tool provides additional safeguards for users. "If we learn that an ad is in conflict with laws or regulations, our expectations or our guidelines, we take action to remove it from the Exchange as quickly as possible," the company stated.

But Edelman contends that whereas the Media Guard ad classification system used to categorize certain ads as deceptive, it no longer does.

"Right Media renamed the 'deceptiveness' category of characteristics — now calling those categories 'ambiguous or unclear attributes,'" he wrote in his report, suggesting Right Media's first classification system was more straightforward — but the new nomenclature appears designed to deceive.