> What fundamental good does spreading any PoW to millions or billions of devices accomplish? Nothing. Well, if the owners of those devices control the mining

> What fundamental good does spreading any PoW to millions or billions of devices accomplish? Nothing. Well, if the owners of those devices control the mining they're doing, then it secures the network by preventing a 51% attack from any single miner with enough power. But in this case, only the website operator benefits by not having to pay for electricity.