Quote Originally Posted by 'ahtremblay',index.php?page=Thread&postID=151190#p ost151190
In the US, the last 4 digit of your credit card is your zip code, so the blizzard page checks for it.
This is not correct. The credit card number is a combination of several different fields, the last number of which is a checksum of the other digits. http://en.wikipedia.org/wiki/Credit_card_numbers.