hi, firefox hello is based on the webrtc standard, which enables peer-to-peer communication between two browsers. so only two people can communicate in hello at the same time...

To expand on the previous answer, although its generally peer to peer, there's further work being done on the WebRTC standard and platform that will allow multiple peer connections.

Hence, at some stage Hello is likely to be expanded to multiple people, but at the moment it is only 2 people - that's the experience we're focusing on optimising first.