Problem with ATM cards is, all the small overdrawn amounts will be paid -- so a small $3 cup of coffee will cost you $35 plus the amount they loan you, even if it is 10 cents.
I know someone who ran up a $750 bill in fees, that go up weekly with futher penalties.
So you really have to watch the balance closely -- since this is where the bank is going to make a huge profit off you.
However, the pre-paid credit cards may limit you to 16 like mycard.ca does.