Opportunity cost
Energy is a scarce resource. If significant energy is wasted on cryptocurrency mining, that energy can't be used for something useful. If more capacity is added to meet the increased demand, then presumably all energy consumers end up paying more to cover the costs of building the extra capacity. I don't see why I should subsidise the activities of greedy speculators, who provide no benefit whatsoever to society. And if their increased energy usage actually results in an overall energy shortage, and power cuts, then it is about time to shut them down.
I have yet to see any solid arguments saying why this inefficient method of processing financial transactions has any advantage over conventional banking. If we think banks are over-charging for international transactions, then that might require regulation, in the same way that most banking activities are heavily regulated.
Biting the hand that feeds IT
