Dr. Mike Walden, North Carolina Cooperative Extension economist in the College of Agriculture and Life Sciences at N.C. State University, responds:

"Well, not really. And this is where I think a lot of people are surprised. Of course, it used to be that you could cash in, so to speak, your cash - your dollars - for gold, but that's been long gone. Now there is a legal stipulation that dollars and coins printed by the U.S. government must be accepted as payment. But I think the real reason that the merchants that you talk about take your paper money, the real reason they do that, is simply trust. They trust that everyone else will take that paper as payment. So when they turn around and buy something, that person that they are buying from is going to take that paper money.

"And I think the trust is based really on two things. Firstly, the U.S. government isn't going anywhere. We have had a very stable government for, really, our entire history virtually. And there's no signs of any threat of an overthrow of the U.S. government. So that U.S. government-issued cash is still going to be used as legal tender.

"And I think the second reason that people take paper money as payment is they understand the purchasing power of that payment is not going to dramatically change over a short period of time. That is, inflation isn't out of control. Now if we had inflation rates of 25 or 30 percent or even higher - and there have been situations in other countries where they have been that high - I think you would have an issue with people taking paper money. But we have relatively low inflation rates. I think that is one of the big reasons why we do have a paper money economy."