For decades, credit cards have been a means by which large banks have loaned money to poor people at interest rates approaching infinity, read an article on Cracked.com with a nice infographics:
Incredibly, the above isn’t an exaggeration. There are people in this situation right now where each payment to their credit card company leaves them owing more. Only in the last few years has the government moved to stop banks from putting people in this cycle of infinite repayment (where the interest and fees are more than the monthly payments).
How was this ever legal?
Well, in the late 70s, the US Supreme Court ended the federal predatory lending laws, and the credit card economy was born.
Banks issued cards to anyone and everyone, often charging 24.99% interest (or higher, cash advances often collect 29.99%) and adding on an assortment of fees hidden in the fine print. This appears to be a good deal for the card holder, as the monthly payment is very low. Specifically, it was often 2% of the balance, an amount that would either have the card holder paying back their debt many times over or, in the worst cases, never paying it back at all (especially once unexpected fees were thrown in).