Bitcoin has enjoyed a strong surge in support over the past few months, but a sudden drop could spell disaster. As the cryptocurrency surged from a price just under $1,000 in January up to nearly $20,000 in December, it feels like the good times could continue well into the new year. If people start panicking, though, it would be tough to get the money out in time.

Jim Edwards, editor-in-chief of Business Insider UK, thinks it could be horrific:

As anyone who remembers the market crashes of 2000 and 2008 knows, these things happen fast. Billions get wiped from the market in minutes. People who need to cash out now but are an hour or so behind the news can lose their shirts. It is brutal. And blockchain, the technology underpinning bitcoin, just isn’t equipped to deal with it.

Edwards points to a number of factors that suggest a bitcoin price drop could spell disaster. Each transaction needs six miners to confirm, average processing time has been gradually increasing, people willing to pay a higher transaction fee get priority, and 40 percent of bitcoins are held by 1,000 people. In short, if the mega-rich want out, it could cause unprecedented congestion and stop people from saving their assets.

Daily transaction amount Bitcoin.com

Rising transaction fees, as well as a fluctuating price, were one of the reasons cited by online video game retailer Steam for why it withdrew support for the cryptocurrency at the start of the month. When the store first started taking transactions in 2015, fees were just 20 cents. They’ve now reached around $20, making it harder to justify.

But it’s not just high fees that would grind the markets to a halt. Exchanges tell Inverse that if the Winklevoss twins ever tried to pull their $1 billion in bitcoin out of the system, just the act of setting up a sell order for several million dollars would cause a sharp decline in the market. Even OTC orders, which involve lawyers and brokers and can rise to a value of $20 million per transaction, would take several weeks to clear the full $1 billion.

The bitcoin market is valued at a staggering $282 billion overall, with the total cryptocurrency market valued at $624 billion. If a crash is coming, it’s going to be tough to fight.