One of the absolute dumbest messes you can get yourself into, where the insanely high interest rates kick in and rape you in the behind while you're not looking. Often caused by the It's not like I'm really paying for it argument, heard time and time again from people who don't understand that they will in fact have to pay for the items they've just purchased. Often the situation is remedied by paying one credit card bill with another credit card, which obviously makes the debt disappear. Just pay the damn bill on time, folks.