Ah, thanks for clearing that up, cool. I thought they were required when you are in a network with a private IP to reach outside world, because there is no full NAT traversal impl, but wasn't quite sure :)
I just checked and you are correct. It seems that at the moment, peers can only sync directly on a local lan and in order to sync over the internet peers need to join a pub. But that is a technicality that will hopefully be solved in the future. Still, it's not a federated protocol because identities are global and the pubs are only used to improve uptime and availability by replicating messages among users. More on the subject here: https://scuttlebot.io/more/protocols/secure-scuttlebutt.html
