UHMMM you know, there's a chance this could be exploited... I think... Not sure...
Basically considering you are outside the map, you can keep walking infinitely.
That cause the world to generate new terrain. New terrain, more space to be stored.
If somebody with speed hacks starts running in a stright line, updating every chunk and generating new terrain, the lobby would weight a lot in disk space.
But that's not really a problem as lobbies restart periodically and not everyone is meant to exit the map...