Probably not any existing systems; you can still finger and thus demand censorship from a block producer, and you end up with situations where you just can’t host the chain anymore because it’s full of pirated MP3s or whatever now.

And they introduce new problems around having to globally replicate everything and thus getting the net performance out of the system that you get from the worst server involved.

If you need to track some kind of root signing key for a whole p2p system, or something, maybe you can stuff it into Ethereum somewhere. But I don’t think you can get very far trying to actually run a service out of a globally replicated database, and even then you’d have hundreds of operators in legal trouble rather than no operator.