Sorry, I didn't intend to sound condescending, though I see how I did. I was responding to your "I do not follow...". I suspect mining expenditure would still

Sorry, I didn't intend to sound condescending, though I see how I did. I was responding to your "I do not follow...". I suspect mining expenditure would still be mostly spent on energy usage, not finding more efficient hardware/algorithms, since mining is an arms race -- when miner A finds a more efficient algorithm, it's only a matter of time before miner B finds it too, and then they're back on level ground competing over energy. But even if this is not the case, I don't particularly care whether the mining expenditure is spent on energy, or developing and manufacturing new mining hardware, or sacrificing goats to a hash-finding deity. Since the amount of mining the network does is set by a price tag (the block reward), and its intent is to make 51%ing prohibitively costly, by definition it must use up some valuable resource. Whether that's energy or human ingenuity or semiconductor production is just an implementation detail but it'll always be a waste. If Bitcoin switches away from proof of work, I'll stop criticizing it for the inefficiency of proof of work.