Verified card numbers sell for ten times the amount unverified numbers sell for. Now they hit up non profit websites and do transactions for a dollar to see if the cards are valid, though because most people who have a stolen card do not have the billing address address verification and zip verification help stop that (along with only allowing a certain number of transactions from the same IP address in a given time, IP's coming from proxy or out of the country, and other things like that). Non profits are targeted because unlike the big commercial sites they may not be closely monitored 24 x 7, and there's no need to stand at a machine someplace and insert card after card and risk getting caught.