The fastest way to fan out messages efficiently between a group is through one node that is always online. I think no decentralized architecture can be more efficient compared to a centralized system.

Again, a social network only needs to know whom to send your message to and need not know about the contents of the message, If USPS opened our letters, would we argue for a decentralized architecture where we individuals ourselves drove around delivering letters in our spare time?

How were so many of us tricked into handing over so much control?