It seems that there is nothing a consumer can do to completely prevent a merchant from putting an unauthorized charge through on their account. Even if that account is closed or you’re using a “single-use” or “virtual” credit card, fraud-prevention cards with disposable credit card numbers that change after you use them once, you’re not 100% secure. How come? Well, we’ll tell ya.
This SlickDeals forum thread talks about how if a merchant manually bills an account, without sending it through their credit card processor to get appropriate authorization, the bank will pay them without question. The good thing is that charges that are received by the bank that come through without an authorization attached are very easy to initiate a chargeback on.
Once again, it is up to the consumer to examine his bills and make sure his ass is protected.