For an example of this in action, see the xkcd forums - http://forums.xkcd.com/viewforum.php?f=53
Basic premise for a standard newbie-ish game is there are two factions, town and mafia, town don't know whose who, and may consist of a few power roles added in to mostly vanilla players. Mafia is significantly smaller, but know who each other are. Game has a day and a night phase. Day phase players make posts and try and figure out whose mafia, and vote to lynch them, thus killing that person. During the night, mafia can talk via PMs, but town can not talk. Mafia get to pick a player to try and kill overnight. The cycle then repeats. There are near limitless variations based on number of factions, power roles, ect, but that is the bare bones of it.
If this is something that would interest you to try, I'd be willing to run a fairly simple game to introduce people to it, but only if there is sufficient interest. Post here with any thoughts, or if interested.