The first issue lies in the extreme volatility of the price of bitcoin. The cryptocurrency has, since its very earliest days, been a highly unstable one, its price surging and collapsing much like that of a penny stock. Even so, the past year has proven unusually volatile, with dramatic day-to-day and even minute-to-minute swings and plunges. Investors crowding into the cryptocurrency—including those putting bitcoin on their credit cards, or taking out equity loans on their houses to buy it—and regulatory interest from governments around the world have helped to drive those fluctuations. And the currency’s short-term volatility has been matched by some longer-term volatility too: The currency’s value surged 1,300 percent last year, and it has fallen by more than half of late.

For Wall Street–type investors seeking to buy and hold bitcoin or risk-happy prospectors looking to make a quick buck, such price swings are generally a feature, not a bug. Nor are they problematic for many the many Silicon Valley entrepreneurs interested in the blockchain technology underpinning the currency. But this kind of volatility is a headache for participants in marketplaces with transactions denominated in bitcoin. That means the darknet markets, which have continued to crop up and collapse since the federal authorities seized Silk Road in 2013.

On those markets, the price of drugs and other illicit and licit goods are fundamentally pegged to dollars or euros, not bitcoin. Buyers think in terms of traditional currencies, in other words: An eighth of an ounce of marijuana is worth $25, not a minuscule fraction of a bitcoin. And vendors think in the same terms, often purchasing wholesale goods with dollars or other government-issued currencies, or seeking to sell their wares for cash in person. As such, “the price of a bitcoin does not matter,” Nicolas Christin, a computer scientist at Carnegie Mellon University and an expert on the darknet markets, told me. “But that it is stable matters.”

To understand why, it helps to know a bit more about the mechanics of buying drugs on the dark web. A purchaser buys bitcoin, reviews vendors’ offers on a marketplace, and then pays for his goods. His money generally goes into escrow before it is released to his vendor. This introduces a number of financial choke points and transaction delays: between when the purchaser procures bitcoin and makes a purchase, when the vendor receives the order and receives payment from escrow, and when the vendor cashes out from the marketplace. Those are all moments when bitcoin’s volatility becomes problematic. For vendors, price drops while payments are in escrow might wipe out all the profits from a sale, for instance.

Complaints about these kinds of scenarios are rife in popular forums where buyers and vendors chat online, including on Reddit. “Seems I hear Vendors are sitting on the sidelines. If payment is in [bitcoin and] then [the] price falls all their work is for nigh,” one user recently posted, worrying that fewer vendors were selling given the market dynamics at work. Another complained, “Seriously?! I purchased coins this morning at like $675 and within 1.5 hours it dropped down to $625.”