last time i checked in the USA credit card fraud is a federal crime- and i'm sure there are a bunch of suits waiting for you to contact them... I believe that would be the secret service? anyway- as posted before- contact the law, they'll help...

/edit->

please tell your customer's that there Account information was "compromised" so that they can take the proper steps to protect their assets... this is serious- as if you do not inform them of this, you can be held somewhat accountable... (please, someone correct me if i'm wrong) but i was under the impression that businesses has certain responsibilities concerning their customers financial information?