Central authority is probably necessary if it is an authority on the final word. But I don't think that's as important as it sounds: what's really important is

Central authority is probably necessary if it is an authority on the final word. But I don't think that's as important as it sounds: what's really important is authority on the first word. A distributed system could use a web of trust where each user claims to be the originator of their work, via PGP signature. At that point "authority" is determined by what user identities you consider trustworthy by including them in your web of trust.