Keynes realised that countries which run persistent surpluses can do harm: they suck up too much of the World’s money which necessarily means other countries have less money, which in turn means the latter countries spend less, which tends to cut demand and raise unemployment. That’s just one example of what Keynes called the “paradox of thrift”.
Same applies in the Eurozone: Germany and some other core countries run persistent surpluses which necessarily means other countries both in the Eurozone and elsewhere must run external deficits.
However, the idea that countries that are persistently in surplus necessarily do harm (an idea that Varoufakis seems to back) is crucially dependent on the assumption that the total amount of money is limited, or at least not flexible enough to counteract the latter unemployment raising effect.
However, as MMTers, Positive Money and others have long pointed out, there is no limit to the amount of money that a government and its central bank can create and spend into its economy. That means that if some group wants to hoard money (and one large group of that sort at the moment happens to be corporations) that shouldn’t be a problem: the central bank just needs to create and spend enough to counteract the deflationary effect of that hoarding. That point applies as much to the ECB in Europe, as it does to the World as a whole and its banker, the US.
Of course, the idea that the US is the World’s banker is not 100% accurate: the World actually has several central banks, with the US Fed being the biggest. That is, the Swiss Franc, the Euro, Pound Sterling and other currencies all act to some degree as international currencies.
To summarise, if central banks and their governments just create and spend enough to keep inflation near 2% (or whatever the target is), then we can forget about surplus recycling, which in any case would be a bureaucratic and politically fraught process. And where inflation exceeds the target, it will be necessary to run the occasional SURPLUS as opposed to a deficit.