Bitcoin, hailed in some quarters as the future of currency, is having a rough week, with a flurry of rumors that China will shut down exchanges and the head of a major U.S bank calling bitcoin a "fraud."
Plummeting prices have again raised questions about the wisdom of owning it, if not its legitimacy.
The digital, or cryptocurrency, tumbled 15 percent Thursday to about $3,300 against the dollar. Bitcoin, which has had bouts of volatility in the past, has shed about a third of its value since Sept. 1. But it's still up about $600 compared with last year at this time.
Still getting up to speed on bitcoin? Here's a quick rundown.
What is bitcoin?