Plenty of MMOs use instances. Although it's pretty fundamental to the genre that a massively multiplayer game will involve shared spaces and content, sometimes it makes sense for a game to create either separate versions of common spaces, or private sub-spaces where the environment is made for a given player or group. Instancing can cut down on lag and overcrowding, by spreading the population of a given zone across multiple versions; it can also serve story goals, by allowing players to have challenges all to themselves instead of waiting in line for their turn at a public challenge.
But instancing can cause problems, too. One criticism of City of Heroes
was that mission maps were always instanced, creating a sense of discontinuity. Age of Conan,
too, has come under fire for overuse of instancing, particularly in PvP zones, where it used to be possible for a player to make a nuisance of himself in one instance and then vanish into another to avoid pursuit.
So, what sort of content should be instanced? Is there such a thing as too much instancing, or should more games be like Guild Wars
which instances just about everything? Does instancing drive you crazy, or make you sigh with relief?