Megan McArdle on the market incentives related to the Playstation identity theft debacle:

I wonder, actually, if this won't muck up the whole market.  After all, credit card thefts work because people don't know that the numbers have been stolen.  But the first thing we did when the network came back up was check whether we'd maybe added a card to the account for some little transaction we couldn't remember.  If we had done, we would obviously have immediately cancelled the card, and we can't possibly be the only people who felt this way.

If we're typical, rather than outliers, than as the thieves attempt to pass these numbers, a high percentage of them are going to be dead cards, or cards that the owners are watching very, very carefully.  That ought to drive prices down even further--even for cards that have been stolen by other means, since I assume that it's hard to establish provenance.