Not to stop the drum roll, but the Governments (as a consortium) can stop (at least Bitcoin). All they have to do is to track down the mining pools, which are becoming increasingly centralised. Tech is here; using heat visors and helis, the same way they track down illegal weed growers. This might cause a systemic shock in crypto economy or it might be a big positive for a Proof of Stake alt coins. Of course at the moment it is highly unlikely due to coordination problem, but is a possibility nevertheless. Black Swan style