PoW was looked at well over a decade ago by Bill Gates personally (and obviously others) It's never been adequately explained why no one implemented it. It mi

PoW was looked at well over a decade ago by Bill Gates personally (and obviously others) It's never been adequately explained why no one implemented it. It might be the obvious, incremental gains from filtering spam have kept users happy enough. No one company wants to take the first hit of educating users and the incompatibility with other systems. It might complex processes like the engineers asked to implement it think users give a shit about mailing lists (maybe they did in 2004 when Gates told Davos he'd kill spam). Maybe marketing drones on about big business in all the meetings, crushing a good idea. Or maybe Microsoft went for micro payments over PoW, not realising micro payments was in itself an impossible dream. Ask Bill next AMA on Reddit.