This is why "serious games" and messaged-based games, in my mind, should never require more than a handful of players (or ideally, 1 or 2) to deliver its rhetoric -- or they should use asynchronous multiplayer -- because this is how a game dies. In contrast, single player games live forever.
I don't want to say, "don't make real-time multiplayer games," because that sounds awful. But I guess I'm saying it. I don't see any way around it.