Depends who the debt is to. Loan sharks and bookies are scam artists. Beat them any way you can. Use the same legal system they'll use when they're in a corner.
And what happens when you owe the government money that you can't pay? Seize your assets, garnish wages, remove money from your bank accounts. You're making every bookie out to be the devil.
An illegal bookie or loan shark doesn't have that kind of leverage. In times of desperation, survival is the game. Ask any bookie or loan shark that gives people up to save his own ass.
