Online ad networks are not the only entities aiding and abetting online pirates. The companies who process the payments for pirate sites are equally culpable when it comes to sustaining online piracy (and profiting from it). PayPal, Visa, American Express, MasterCard and their ilk make it easy for these black market profiteers to process subscription fees.
Filesonic.com website featuring illegal download and payment links for PayPal, Visa, Mastercard, etc.