Early Tuesday, the world's most established exchange for Bitcoin disappeared from the Internet, sending the price of the virtual currency tumbling and prompting fears that the world's biggest experiment in electronic cash could soon be strangled by fraud or regulation.
Here's an explanation of what bitcoins are, how exchanges work, and why the demise of the exchange, Mt. Gox, means many people may have lost a lot of money.
Q: What's a bitcoin?
A: Bitcoins are basically just lines of computer code that are digitally signed each time they travel from one owner to the next. They are the basic unit of a new online economy which runs independently of any company, bank, or government. Because bitcoins allow people to trade money without a third party getting involved, they have become popular with libertarians as well as technophiles, speculators - and criminals.
Q: Who's behind the currency?
A: It's a mystery. Bitcoin was launched in 2009 by a person or group of people operating under the name Satoshi Nakamoto and then adopted by a small clutch of enthusiasts. Nakamoto dropped off the map as Bitcoin began to attract widespread attention, but proponents say that doesn't matter; the currency obeys its own, internal logic.
Q: What's a bitcoin worth?
A: Like any other currency, bitcoins are only worth as much as you and your counterpart want them to be. In its early days, boosters swapped bitcoins back and forth for minor favors or just as a game. One website even gave them away for free. As the market matured, the value of each bitcoin grew. At its height three months ago, a single bitcoin was valued at $1,200. On Tuesday, it was around $500.
Q: Is the currency widely used?
A: That's debatable. Businesses ranging from blogging platform Wordpress to retailer Overstock have jumped on the Bitcoin bandwagon amid a flurry of media coverage, but it's not clear whether the currency has really taken off. On the one hand, leading bitcoin payment processor BitPay works with more than 20,000 businesses - roughly five times more than it did last year. On the other, the total number of bitcoin transactions has stayed roughly constant at between 60,000 and 70,000 per day over the same period, according to bitcoin wallet site blockchain.info.
Q: Is Bitcoin particularly vulnerable to counterfeiting?
A: The Bitcoin network works by harnessing individuals' greed for the collective good. A network of tech-savvy