[quote name='CoffeeEdge']Allow me to enlighten you, then.
The reason that Xbox Live carries a fee, is because Microsoft maintains all the servers for all the games on XBL, instead of the publishers. With online PS3 or PC games, you have the publishers running the servers. This means that as soon as the publishers decide that running the servers is no longer worth the cost, they can, and will shut the servers down.
On XBL, the fee goes to pay for all of the servers, and guarantees that the online functionality for ALL Xbox 360 games (aside from MMOs) will remain intact, regardless of popularity.
Understand now? It's not like MS just charges the $50, because they can. It actually does go to pay for something, and something pretty useful at that.[/QUOTE]
QFT. Great point that there will always be servers. If you want an example of how a community based server system can fail, check out L4D for the PC. There are times where you're trying to get your lobby to find a server but 4 out of 5 attempts will result in joining a server that pings over 100ms or crashes 15 minutes into the game.
Usually Valve's model works well, like in TF2 or CS, but for L4D it has been terrible (though I don't know how L4D's server model is on XBL).
If you want a console example, EA has shut down the servers for several of their games since they were running their own servers rather than using XBL's servers.