Well obviously it isnt fine. Because when you have too many players on 1 server, the communication starts delaying. You cant send information to all 150 players at the same millisecond from only 1 server. While it might be able to handle the task fromt he hardware standpoint, you have the issue that data packets start queuing and the players dont receive the needed data in time. When the packets are delayed by 1-4 frames, thats like 16ms-72ms (not counting the physical connection lag, just packet queuing), thas when having dedicated servers is not better than p2p.
In fact p2p can even be way better than dedicated servers, where multiple instances run on 1 server. When I host in MW3 or any other COD, everyone of my clanmates has close to perfect connection. Their ping to me is like 25 milliseconds on average or better. And hosting a game with only 12 players is no problem for my connection at all. Its a fibreoptic 50/10 with almost LAN quality ping to most of the servers in the country.
