Originally Posted by koland
The CC requirement is just lazy programming (not to check for a zero price) and a remnant of their pre-digital (and free) pre-order system.
That said, it's easy enough for most to pick up a pre-paid card (or generate a single use card from Citibank) and use that as your Kindle credit card.
I've also received Visa cards for bonuses from our phone company (now they do Amazon gift cards), which Amazon accepts as a credit card without an issue.
In addition to this, if you have a credit card on your Amazon account for any other reason, they will not ask for info for a Kindle pre-order, since they have card info on file already.