Although at times I like larger-scale games with multiple players, there is a problem with long waits between turns.
It's not usually an issue with a group of friends, but with a large group of random players in a match, there could be problems with waiting for turns, people leaving/disconnecting and such.
I'm not against the idea, but I can see some very large problems that would need to be taken into account. I know common sense should prevent impatient people from joining a large/multiplayer game, but it is not always the case.