Multiuser Domains, originally Multiuser Dungeons (MUDs) began to emerge almost as soon as multiuser chat systems like IRC came out.A user connects to the central server, assumes the role of a fictional character, and acquires possessions, a home, friends, enemies and lovers as he interacts with other users on the system. Most such systems are set within the context of a mythical past, a high-tech future, or are just a hodgepodge of everything. Most of these systems are coded by their users; once you reach a certain level of proficiency in the game, you become a "wizard" and are bestowed with the power to create new worlds, intelligent monsters, mazes, puzzles, weapons, items, and quests. The MUDs that have been around for more than a year or two acquire a distinct and diverse set of communities that may war, collude, or cooperate. Such MUDs are often mind-bogglingly huge in size; every day they may gain a whole territory with hundreds of locations; it would be impossible for a single user to ever explore the entirety of the MUD. More recently, several attempts have been made to create commercial and graphical MUDs - Ultima Online is the most popular such example. Their easy-to-use graphic interface and widespread marketing may well bring MUDs to the masses.
IRC IRC, or Internet Relay Chat, is decades old and allows users to enter virtual "chat rooms" that can range from being completely empty to being filled with hundreds of chatting people. It remains popular to this day, a hangout for enthusiasts, sex fiends, and hackers. America Online uses IRC-like technology in its own implementation of Chat Rooms. On nearly all MUDs, you are not required to identify yourself to the system. The only way that people know you is through a pseudonym with which you identify yourself. This gives the impression of anonymity; as mentioned in Wired many users find MUDs a way to vent violent feelings in ways otherwise socially unacceptable, such as brutally slaughtering creatures or other users, raping users, or assuming the role of the opposite sex. However, there has been at least one case in which a MUD user has their account removed for raping another MUD user online; that is to say for describing in written text the act of a rape. It is not difficult to track down a MUD user; an administrator just needs to look at what machine the given user has connected from; most Unix systems will even reveal what user is logged into another machine. The MUD's administrator can then easily contact the administrator of the machine from which the user logged in and ask for more details about that user's account.
While one could certainly argue that crime happens in real life as well, it seems clear that online users who believe themselves to be anonymous more often act in an irresponsible fashion: after all, they are not accountable for their actions. (This will be discussed later in the ethics section.) Some could argue that this shows that the online world encourages evil, but the argument goes both ways: it doesn't yet seem that there is a harm to people cutting each other to bits online. Many, including this group, find it cathartic to blow up a few strangers (and be blown up a few times in the process).
On most MUDs, anonymity is the norm; it's considered rude to ask people what their real name is or where they're located. It's only when you really get to know someone really well that they will consider disclosing such information to you, and even then it's impolite to ask for it. The system allows people to live a powerfully imaginative existence and stripping back the figurative curtain from the Wizard of Oz is generally considered rude.