I know someone who works for an insurance company that covers credit card and identity fraud. They are actively monitoring these sites for their costumers information. Even though that's a private company, I wouldn't be surprised if government organisations do the same.

And following LeCarré, I could easily envision some entities searching for and holding certain of these acquired credit card numbers in reserve, should there be a need to charge p*rn or some financially questionable charges onto those account holders they care to call into question.