When the virtual currency bitcoin was released, in January 2009, it appeared to be an interesting way for people to trade among themselves in a secure, low-cost, and private fashion. The Bitcoin network, designed by an unknown programmer with the handle “Satoshi ­Nakamoto,” used a decentralized peer-to-peer system to verify transactions, which meant that people could exchange goods and services electronically, and anonymously, without having to rely on third parties like banks. Its medium of exchange, the bitcoin, was an invented currency that people could earn—or, in Bitcoin’s jargon, “mine”—by lending their computers’ resources to service the needs of the Bitcoin network. Once in existence, bitcoins could also be bought and sold for dollars or other currencies on online exchanges. The network seemed like a potentially useful supplement to existing monetary systems: it let people avoid the fees banks charge and take part in noncash transactions anonymously while still guaranteeing that transactions would be secure.

Yet over the past year and a half Bitcoin has become, for some, much more. Instead of a supplement to the dollar economy, it’s been trumpeted as a competitor, and promoters have conjured visions of markets where bitcoins are a dominant medium of exchange. The hyperbole is out of proportion with the more mundane reality. Tens of thousands of bitcoins are traded each day (some for goods and services, others in exchange for other currencies), and several hundred businesses, mostly in the digital world, now take bitcoins as payment. That’s good for a new monetary system, but it’s not disruptive growth. Still, the excitement is perhaps predictable. Setting aside Bitcoin’s cool factor—it might just as well have leapt off the pages of Neal ­Stephenson’s cult science-fiction novel Snow Crash—a peer-to-peer electronic currency uncontrolled by central bankers or politicians is a perfect object for the anxieties and enthusiasms of those frightened by the threats of inflation and currency debasement, concerned about state power and the surveillance state, and fascinated with the possibilities created by distributed, decentralized systems.

Bitcoin is not going to make government-backed currencies obsolete. But while the system’s virtues, such as anonymity and the lack of bank fees, may not matter much to most consumers, one can envision it being useful in a variety of niche markets (some legal, others not, like recreational drugs). Where anonymity is valuable, where trusted third parties are hard to find or charge high rates, and where persistently high inflation is a problem, it’s possible that bitcoins could in fact flourish as an alternative currency.

Before they become such an alternative, though, the system will have to overcome a major, and surprising, problem: people have come to see it primarily as a way to make money. In other words, instead of being used as a currency, bitcoins are today mostly seen as (and traded as) an investment. There’s a good reason for that: as people learned about Bitcoin, the value of bitcoins, in dollar terms, skyrocketed. In July 2010, after the website Slashdot ran an item that introduced the currency to the public (or at least the public enthusiastic about new technologies), the value of bitcoins jumped tenfold in five days. Over the next eight months, the value rose tenfold again. This attracted an enormous amount of publicity. More important, it also made people think that buying and holding bitcoins was an easy way to make a buck. As a result, many—probably most—Bitcoin users are acquiring bitcoins not in order to buy goods and services but to speculate. That’s a bad investment decision, and it also hurts Bitcoin’s prospects.

True believers in Bitcoin’s usefulness prefer to deny that speculation is driving the action in bitcoins. But the evidence suggests otherwise. The value of the currency has been tremendously volatile over the past year. A bitcoin has been worth as little as a few pennies and as much as $33, and after seeming to stabilize at around $14 over the summer, the bitcoin’s value tumbled by almost 50 percent in a matter of days in August. Media coverage has had an outsized impact on the value of bitcoins, even when it has not had a major impact on the number of transactions conducted. Blog posts in which people talk about buying bitcoins because of how much they’ve increased in value are common. In May, Rick Falkvinge, founder of the Swedish Pirate Party, which focuses on patent and copyright reform, posted that he had decided to put all his savings into Bitcoin. Although he had previously published a series of posts arguing for the bitcoin’s viability as a currency, his first listed reason for investing in bitcoins was that their value had risen a thousandfold against the U.S. dollar in the previous 14 months. That’s classic speculative thinking.

The problem with having the Bitcoin economy dominated by speculators is that it gives people an incentive to hoard their bitcoins rather than spend them, which is the opposite of what you need people to do in order to make a currency successful. Successful currencies are used to transact day-to-day business and lubricate commerce. But if you buy bitcoins hoping that their value will skyrocket (as anyone investing in bitcoins would), you’re not going to be interested in exchanging those bitcoins for goods, since then you’ll lose out when the value of bitcoins rises. Instead, you’re going to hold onto them and wait until you can cash out.

This kind of hoarding is made more likely by the way Bitcoin is set up. Whereas the supply of modern, “fiat” currencies is controlled by central banks, the supply of bitcoins is permanently limited; there will never be more than 21 million bitcoins in existence. (The total number of coins is a result of the system’s initial rules governing how many bitcoins miners could earn, and how often.) Bitcoin’s limited money supply is one of the things that people like about it: the currency cannot be debased, as money can when central bankers print more of it. But the flip side is that if the demand for bitcoins rises, for whatever reason, then the value of bitcoins will necessarily rise as well. So if you think that bitcoins are going to become more and more popular, then—again—it’s foolish to spend your bitcoins today. The rational thing to do is hoard them and eventually sell them to new users. But that means there will be fewer bitcoins in circulation (and more in people’s virtual wallets), making them less useful as an actual medium of exchange and making it less likely that businesses and consumers will ever see Bitcoin as legitimate.

Now, even traditional currencies can be subject to this kind of cycle, which economists call a “deflationary spiral”—although with conventional currencies, the cycle occurs when falling prices lead people to start hoarding cash in the expectation that prices will keep falling (which in turn holds down demand and makes prices fall further). The quintessential recent case is Japan after its real-estate bubble burst in the 1990s.

With ordinary currencies, though, there’s a limit to how far down the spiral can go, since people still need to eat, pay their bills, and so on, and to do so they need to use their currency. But these things aren’t true of bitcoins: you can get along perfectly well without ever spending them, so there’s no imperative for people to stop hoarding and start spending. It’s easy to imagine a scenario in which the vast majority of bitcoins are held by people hoping to sell them to other people.

We may already be living in that scenario, since despite all the buzz about Bitcoin, the number of actual transactions conducted in bitcoins, and the value of those transactions, has been shrinking. According to bitcoinwatch.com, the best source of Bitcoin data, more than a million dollars’ worth of bitcoins were traded on June 13. By early August, less than half a million dollars in bitcoins were being used in transactions; even the currency’s value had been cut in half. Successful network technologies do not tend to see usage plateau, let alone shrink, this early in their history. And the lack of growth in the number of transactions conducted via Bitcoin is not what you’d expect to see if the technology were, as Falkvinge said, on its way to being a part of “normal daily commerce.” It’s true that there aren’t all that many goods and services one can (or would want to) buy with bitcoins. But in a way, that’s the real problem: a falling rate of use makes businesses less, not more, interested in accepting bitcoins, and ordinary consumers less interested in spending them.

So just now the bitcoin boom of the past year looks not so much like the birth of a new currency as like a classic bubble. And this has created a real paradox for bitcoin enthusiasts. The best thing for bitcoins would be for people to stop thinking of them as an investment and start thinking of them as a currency. That probably requires the bubble to burst, as it may be doing right now. But if the bubble bursts, it’s possible that people’s interest in Bitcoin will just fade away. After all, would you accept bitcoins in exchange for your work or products if you knew their value had fallen 50 percent in a matter of days? The challenge for Bitcoin now is whether, having become popular because of the cycle of hype, it can somehow avoid being devoured by it. Only then might we be able to say, Good-bye, asset; hello, currency.