Hailed by The New York Times as a "guru to Wall Street's gurus," value investing expert Bruce Greenwald takes some time to offer his insight and advice to The Motley Fool. A professor at Columbia University's Graduate School of Business, Greenwald has also written multiple books, including Value Investing: From Graham to Buffett and Beyond.

In the following video, Greenwald examines the definition of money -- as a medium of exchange, a measure of value, and a unit of account -- and then looks at how Bitcoin fits, or doesn't fit, each of those meanings.

Full transcript below.

Matt Koppenheffer: Let me finish up with kind of a fun one here. We heard Cameron and Tyler Winklevoss, the Winklevoss Twins, talking about Bitcoin. They're backing and have gotten involved in Bitcoin. Do you think that this is something that has legs, maybe can steal some market share from traditional banking?

Bruce Greenwald: I don't think it's traditional banking. Don't forget that what traditional banking does is, it enables you to write checks or do wire transfers. There is a transaction infrastructure.

If you go back to the traditional definition of money, it's as a medium of exchange, it's as a measure of value, and it's as a store of value. It's a unit of account, it's a medium of exchange, and it's a store of value.

It turns out, as a unit of account, nobody's going to price anything in bitcoins. It's always going to be the currency, because that's just the dominant way to do it, and there are big network effects from that. It's very hard to get people to change.

In fact, they measure the value of bitcoins in -- you guessed it -- dollars, or whatever currency it is, so you're not going to get it as a unit of account.

It's not a medium of exchange. You don't have to keep a bitcoin balance to pay your bills, so what you're left with is a store of value.

We've got lots of stores of value. We've got gold, we've got all sorts of other kinds of real assets that you can have. We have inflation, we have TIPS, we have all sorts of real stores of value that are probably more liquid than the bitcoins, and are less easy to manipulate, and are less subject to insider trading.

Look, in the old days every bank used to issue its own currency.

Koppenheffer: Oh, right. Yeah.

Greenwald: It was very unstable what the relationships between the currencies were. Having lots of different bitcoins has a lot of the flavor of that, but it's got no natural advantages over gold or any other real measure of value.

Koppenheffer: It's fun to talk about in the meantime.

Greenwald: I think there's a rule. If the Winklevoss Twins are talking about it, it's almost certainly opportunistic, and they almost certainly are not the people who know how to make money out of that idea, as Facebook showed.

Koppenheffer: That's very fair.

Greenwald: You don't want to invest with them.

Koppenheffer: All right, Professor Greenwald we really appreciate you talking to us. Thank you so much.

Greenwald: It's always a pleasure to talk to you guys!