I would add to that that the only part that requires this proof of work when decentralized is the timestamping. We can have a system where everything is decentralized with a timestamping subsystem (that can also be composed of many computers for a balance of power) that blindly timestamps transaction hashes without even knowing what it is timestamping so that it cannot censor it. This would be a perfectly reasonable system for me and one that would spare that huge cost of electricity burned on proof of work.