But technically speaking it really isn't a big deal, if you take any one of your own credit cards, extract the 'bin' and generate the rest of the numbers to be valid (http://en.wikipedia.org/wiki/Luhn_algorithm) you can make credit card numbers until you drop, with a high probability that they are currently in service (if your number is active, so are a lot of other numbers in your bin).

But those numbers alone will not allow you to do anything.