Even if you weren't one of the 2.2 million people whose credit card was potentially ripped in the Sony PSN debacle, there's still a good chance you've had your credit card data ganked before. What happens after your data's been stolen? It's sold.
Often in underground forums, for $US5-$US10 per stolen card. A crazy side effect of the the massive breach is that if 2.2 million numbers are dumped on the stolen credit card market, the excess supply will push the price of stolen cards down to $US1 or $US2. Somehow I don't think that'll make you feel any better. More info at Bits.