Say you're self-employed and your best client suddenly stops paying. They have a good track record and assure you it's just a technical blip or something. You have bills to pay so request an increase in credit limit. Then your client's blip turns into something much worse, and on it goes...

That's how people become unstuck. Very few people start off with bad intentions.

"But it's more dangerous than using a debit card where a stolen card ties up real money during the dispute window."

That's true--my solution to this is not keeping too much money in my checking account.