From my quick read of the spec, server-to-server federation assumes that servers can be trusted. That need not be the case; unless a message is signed it should not be assumed to have come from a specific user. I don't know if there's an easy way to share keys in a decentralized way, but that'd be an interesting problem to solve (some blockchain maybe).
The other question is whether we want server-to-server federation at all instead of a P2P network like bittorrent. With the decreasing cost of compute, I am also optimistic of everyone being able to run a little sandbox on the cloud to exchange data with others, instead of routing it via FB/Twitter.
The other question is whether we want server-to-server federation at all instead of a P2P network like bittorrent. With the decreasing cost of compute, I am also optimistic of everyone being able to run a little sandbox on the cloud to exchange data with others, instead of routing it via FB/Twitter.