I've never heard of this, and yet I've read a number of think-pieces that have been on the front page lambasting the ad networks for letting sketchy ads through. If this is only the trivial end of hiding from the network's policing strategies, it seems like they're a lot less culpable than I thought. Do you have links to more information on the other tactics?
You can Google "PPC cloaking" and get quite a few interesting results. There are also professional cloaking services that maintain large IP datasets. The two most popular of those are called Just Cloak It [1], and, ironically, FraudBuster [2]. Also if you're looking in general for information on this and other black/grey hat marketing techniques, Black Hat World [3] is a great place to start.
Come on, we're talking about Facebook? They could easily "sample" the actual ads that are displaying for users on their computers, and compare them to the ones that were approved.
