1) So on energy usage of BTC:
The profile will change long-term. Right now the main driver is from block rewards.
But as block rewards exponentially decay, those will become less relevant.
Long-term, there are really two core drivers.
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4) The payoff from attacking the network scales roughly linearly in BTC price (market cap and/or $ value of xfers per block).
So I think this scaling is similar to the tx fee scaling.
