The card in question is a VISA, if that's of any importance. I've noticed this only on Amazon. All other sites I've purchased something from, ever, have needed the CVC code for the card. However, I know I never entered the CVC on Amazon when I added my card to it, and this has been bugging me ever since. How do they successfully charge the card without the CVC code?
That code isn't necessary. This may cause more fraud and more chargebacks, but Amazon keeps those numbers low so that they can offer a faster shopping experience such as one-click.

The only thing necessary to make a purchase is the card number and, in all but rare cases, expiration date, whether in number form or magnetic. Most systems require more information (such as matching full name, bank phone number, physical billing address with zip code, et al) so that they can deal with fraud and/or chargebacks, and sometimes this is enforced by the issuing bank.
