Wow - I didn't expect cold, hard cash to be the majority when I started this poll. I was expecting credit cards, or at least credit+debit, to be the majority.
The inconvenice of not having a credit card for me is that I can't buy most things on the Internet without one...which is good from the point of forcing a degree of fiscal prudence, but not helpful when trying to buy airline tickets home. So eventually I figure I'll have to get a credit card at least for those circumstances.
Thought of a question on this topic earlier today: how much would you have to withdraw to bankrupt the ATM machine? Obviously they can't have an infinite amount of money, but they must have a good amount.