I'm near Boston, and my verizon FIOS is 20/10Mbps, which is very fast :-D
But honestly, with 16 users doing things, and 2+ people joining at the same time, there is lag. Keep in mind, when you have 10 people on a server, seemingly regardless of your bandwidth, one bad apple (40+ping) ruins everybody's gaming experience.
Screw adding more people to a server, I say, make the game load without lag for those joining. That's always been a huge problem for my servers- Downloading maps and updates is pityfully slow, and so is loading all the bricks, and it causes lag unjustly for other players.