Facebook’s proposed cryptocurrency, Libra, would make it a lot easier for hot money to move around the world. Speculators are always looking for the next big thing. One of the most painful side effects of the past 10 years of unconventional monetary policy has been the tendency of investors looking for yield in a low-rate world to pile into the latest bubble — whether it’s emerging markets, commodities or junk bonds. That’s why countries such as Brazil and Thailand, for example, have sometimes resorted to capital controls to stabilise their financial systems, a move that even the IMF now sees as legitimate.

Facebook wants to do just the opposite — to grease the wheels of global capital flows with a digital coin that operates outside the existing central bank system. Its stated aim is to facilitate the “global, open, instant” movement of money across borders with a privately managed cryptocurrency headquartered in Switzerland that will somehow engender worldwide financial “trust” and “inclusion”.

Let’s put aside, for the moment, the assorted oxymorons in Facebook’s statement, as well as the technical and regulatory hurdles that it