As a possible victim I prefer spreading the list as quickly as possible. All major commerce sites and payment companies will take note of this and stop accepting these card accounts.
Obviously it will still be a huge hassle to reissue all those cards but it will minimize the financial damage.
I think once that file was online even for a few minutes, the card numbers mentioned in it are not safe anymore. It will be leaked again.
If it's not some kind of provocation (files with false data) then this is a pretty big crisis. I'm going to have to monitor my credit card logs closely in the next few weeks...
I was expecting some kind of code-golf mark for that challenge though. There are many ways to solve it.