Since City of Heroes shut down - or even since the announcement, really - I've wondered about how to make MMO games robust against that kind of existential threat. When such games become unprofitable, development ceases and the servers are shut down. That's just business. The obvious answer to that problem is to host the game itself on a peer-to-peer network of player machines. Then, no matter how much the game grows or shrinks, there's always enough server capacity.
However, running a game like that on a peer-to-peer network raises some other challenges. For one, there's the matter of trusting the server code and preventing cheating. If the players, technically, have access to all the server code running on their own machines for each other, there's no central, trusted arbitrator for tasks like random number generation and application of the rules. I've outlined before how some trust can be established between peers for generating random numbers, so it's possible it could be worked around, but it requires a lot more communication than an implicitly-trusted server does. It's also probably not the full story for everything that's needed for a trusted peer network of this type.
Still, I'd like to see it attempted, if only to know that, in the future, there's a definite way to save these games from destruction when they become unprofitable, or for smaller, niche games to get a leg up when they're starting out and can't afford dedicated server hardware.
Mokalus of Borg
PS - On the City of Heroes front, a new game called Valiance Online has started open public testing.
PPS - Which is a long way from a complete game, but more than I've seen in a while.