Would you want everyone to know every business you buy something from, however innocuous? I’m going to guess no. Think of this prospect as similar to how Gmail gives its users more than enough space to store every email they ever send or receive, meaning that I now have 10 years — a whole third of my life! — stored on servers. The long-term, mainstream adoption of cryptocurrencies would mean accepting the idea that, at any moment, your entire purchasing history could be revealed to the world at large.