Most startling about the Adweek report was its implication that even
Additionally, Yahoo's targeting platform Genome has sometimes published ad impressions in questionable corners of the internet, like the file-sharing site MediaFire and ad networks like eHealthcareSolutions and Blackboxmedia.
What makes the growing problem of ad fraud, which one web security firm estimates has cost advertisers $6 billion, so difficult to rein in is that it's not clear which parties have an incentive to stop it.
Brands have long seen ad fraud as a cost of doing business, and publishers actually benefit from the pumped up numbers delivered to them by click farms because they can then charge higher advertising rates. As Shields points out, ad buyers are similarly dis-incentivized to get their hands dirty curbing fraud because it makes them look stupid for buying fake impressions in the first place.
Head over to Adweek for the rest of Shields' sweeping overview of the fraudulent advertising ecosystem.