As it turns out, while few people want to use Bitcoin as a currency, plenty want to treat it as an investable security, similar to gold or silver, especially while the price keeps rising.

I assumed that the blockchain would eclipse Bitcoin itself.

One of the earliest predictions among Bitcoin skeptics and boosters alike was that Bitcoin itself would be just a predecessor technology to the real, lasting innovation: the blockchain — the peer-to-peer ledger system that records cryptocurrency transactions and allows them to operate without a central authority. I agreed, thinking that the blockchain had real promise, but that Bitcoin would ultimately fade away.

Four years later, there has, in fact, been enormous hype around blockchain projects. (One British company added the word “blockchain” to its name and saw its shares immediately jump nearly 400 percent.) But that frenzy hasn’t detracted from investor enthusiasm for Bitcoin itself — in fact, it has amplified it. And the potential applicability of blockchain technology to all kinds of different industries, from auto manufacturing to insurance to groceries, has inspired lots of non-techies to learn about cryptocurrencies, and served as an intellectual on-ramp for new Bitcoin investors.

I assumed that regulators would crack down faster.

In the frontier days of cryptocurrency, it seemed that every other story was about how criminals and tax-evaders were using Bitcoin to buy and sell illegal goods and services. A huge dark-net narcotics market, Silk Road, was broken up, and its owner was sentenced to life in prison. Several large cryptocurrency sites suffered hacks and thefts. It was easy to think that these problems would lead regulators to take swift action against Bitcoin.