Most of the public cards are bought in CC shops and they have a policy which is that they allow you to try the card and check it before 3/5/10 minutes (time depends on the shop). So, the CCs posters use the card for themselves and then post it in the forum, so the card gets "killed", which means that the card gets blocked by the bank, so the CC shop checker gives a "dead" result, and the CC poster gets his money back, so he can buy, get and post more cards with the same money, without actually spending it unless the checker give a "live" result.
