What Libra backers are calling “decentralisation” is in truth a shift of power from developing world central banks toward multinational corporations and the US Federal Reserve and the European Central Bank.Developed world central banks will understandably prioritise their own economies. Meanwhile, the fewer rupees or lira a country’s citizens hold, the less power the national central bank has to set monetary policy, making it harder to stimulate the local economy in times of economic stress.In the recent Greek crisis we saw first-hand what happens when emerging markets prematurely give up local control of their currency. As a member of the eurozone, Greece lacked control over its monetary policy and had no way to appropriately devalue its local currency after the financial crisis. A decade later the Greek economy is still 25 per cent smaller and its unemployment rate is the highest in the eurozone. Libra could render other central banks equally powerless in the face of recession.The Libra Association could also wield significant power over the workings of global finance. Unless regulators jump in quickly, these for-profit companies will set the standards for identity verification, at least in the short run, as well as defining the rules and enforcement around the privacy of transactions and what to do in case of theft.Facebook and its partners will decide which banks, payment processors and distribution agents to work with, making or breaking companies in some markets overnight. This will entrench existing players rather than creating a truly decentralised system.Many will say these fears are overblown: it’s not clear if Libra will even get off the ground. But if we’ve learnt anything about Facebook, it’s that we should not underestimate its power to transform how people interact. The company’s decision to offer live broadcasting made it possible for teenagers to stream bullying, terrorists to livecast an execution and a gunman a mass shooting. It has similarly transformed mobile messaging and news and journalism faster than many imagined.Governments around the world cannot afford to adopt a wait-and-see approach. The G7 has already set up a working group to review the project in conjunction with the IMF and central banks. Regulators in emerging markets should slow down Facebook’s push by preventing local banks and payment processing networks from accepting Libra. If a Libra user can’t move the coin into a local bank account or cash it in for local currency, it’s unlikely to take widespread hold. This need not be a permanent ban. It simply buys time for all of the implications to be thought through.At the same time, US and Swiss regulators have a central role, for they are likely to be the ones setting standards for know-your-customer, anti-money laundering and financial stability requirements. Watchdogs have underestimated Facebook’s power in the past, allowing it to swallow potential rivals Instagram and WhatsApp. This time the scrutiny by the appropriate government regulators should be nothing short of exhaustive.