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> I disagree, if 97% of servers at AWS were there for some hand-wavey notion of 'providing security' without quantification I think Amazon would be roundly mocked.

Again, you fail to understand that the number of a machines that find a block could be changed by making the blocks smaller. You could do that by also reducing block size to keep the total number of transactions the same. But the larger point is that mining pools make it so that mining machines are paid for partial work, even without finding a block. This enables the utility of mining to be measured by hash rate, rather than by number of blocks solved.

You called it a gray goo style positive feedback loop. It is not, there is a upper bound on how much will be spent. There is no feedback loop as well, if the price goes up, more will be spent on mining, but that does not feedback to make the price go higher as required for a loop. Moreover, the block reward is exponentially decaying.

Your reading of the tweet is that a person saying a system should use less CO2 implies that person believes the system is unsustainable. I don't think that is reasonable, e.g. an Airline CEO launching an initiative to reduce the airlines CO2 usage would not believe that the airline is unsustainable. I did misread the other part of your statement-- you said bitcoin is ridiculous, not that Hal said that.