Most webdevs are familiar with contacting an infringing site and serving a DMCA complaint to a web host or search engine. This US lower court ruling lends weight to my occasional practice of contacting a copyright infringer's third party ad networks. Given successful results (ads pulled from offending page(s) or entire site) perhaps ~15% of the time before the ruling it will be interesting to see if it increases over the while.
A district court judge in Massachusetts said that ad networks that have knowledge of infringing activity and provide an "essential" service that helps website operators enable that infringement on a "massive scale" can be found liable for that infringement if they are "intimately and causally involved in a vast number of infringing transactions".
Claire McCracken, a technology law expert with Pinsent Masons, the law firm behind Out-Law.com, said: "Though the court in this case found that Chitika was, like Visa, not responsible for contributory copyright infringement on the site it does potentially open the way for ad networks to be found responsible in some future cases, most notably in cases where rights holders directly notify ad networks that infringement is taking place.
"This means that ad networks and other business support service companies must be very careful how they treat such warnings, Had Elsevier served a takedown notice on Chitika it is likely that the knowledge requirement would have been fulfilled. It would then have been for the court to determine whether the ad network had substantially assisted in the alleged infringement" she said.
Note: I would not go the ad network complaint route until the others mentioned have failed to discourage the idjits. A further complication: as social media traffic grows simply closing down their SE traffic or causing them to change hosts or domains may not be sufficient deterrent.