As far as I understand (and I could be wrong), your machine does not actually generate money, but merely defers payment until some future date. It does so by essentially exploiting a bug in the Kindle + Credit Card system, and it has an upper limit of whatever your max credit line is. My guess is that if this trick becomes popular, someone will patch the bug (probably Amazon, credit card companies are pretty slow).
So, don't get me wrong, it's a nice hack, but it's hardly perpetual or earth-shattering. One similar trick I know of is to have several credit cards, and use them to keep transferring the balance between them before interest accumulates; but this is less efficient, since the "free balance transfer" special offers occur relatively rarely.
The hack generates money if you invest the "loan" into something that pays interests in less than a month. Not enough money to be worth your time, of course; but it's still infinite free money for a given value of "infinite".
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.