Bitcoin’s wild ride may not have been the biggest business story of the past few weeks, but it was surely the most entertaining. Over the course of less than two weeks the price of the “digital currency” more than tripled. Then it fell more than 50 percent in a few hours. Suddenly, it felt as if we were back in the dot-com era.

The economic significance of this roller coaster was basically nil. But the furor over bitcoin was a useful lesson in the ways people misunderstand money — and in particular how they are misled by the desire to divorce the value of money from the society it serves.

What is bitcoin? It’s sometimes described as a way to make transactions online — but that in itself would be nothing new in a world of online credit-card and PayPal transactions. In fact, the Commerce Department estimates that by 2010 about 16 percent of total sales in America already took the form of e-commerce.

So how is bitcoin different? Unlike credit card transactions, which leave a digital trail, bitcoin transactions are designed to be anonymous and untraceable. When you transfer bitcoins to someone else, it’s as if you handed over a paper bag filled with $100 bills in a dark alley. And sure enough, as best as anyone can tell the main use of bitcoin so far, other than as a target for speculation, has been for online versions of those dark-alley exchanges, with bitcoins traded for narcotics and other illegal items.