I remember when I was 18 at college there was constantly Credit Card companies setting up tables right off campus giving out free stuff if you signed up for a card.
I signed up for them constantly under my parents address and told them to cut up any credit cards that came in the mail. Took over a decade before any were closed due to inactivity but in the meantime I had an 800 credit rating right out of college because I had a crazy balance of unused credit.
I think I had north of 20k available between all the cards, just never used them because interest was like 20%.
It would have been very easy to fuck around and waste a lot of money.