It might be dumb to argue over the semantics, but the substantive debate is worth having. An MMO that uses WoW instances is going to be a different experience than an MMO that only spawns a copy of a dungeon once there are 5-10 groups inside of it. Then there is the related discussion of servers: do you cram everyone on one server and use some form of instances to control population in a given area, do you use multiple servers to control population, or do you use a combination of both?