[jedbrown]

It's easy to steal a card, but the card companies do pretty good fraud analysis and in any case, the card owner is never responsible for the fraudulent charges. Of course the cost of the fraud monitoring and insurance system are passed on to merchants and those who carry a balance. But if you don't carry a balance, there is no question that a rewards card is the best available payment mechanism. If you use something else, you are subsidizing those who use rewards cards.