What is the difference between MMO's (Massively Multiplayer Online games) and Virtual Worlds?
Generally speaking, MMO's use client side software more extensively, but many, many VW's do as well, including Second Life, the granddaddy VW.
MMO's usually have a single, overriding game element. Virtual Worlds usually revolve around a number of smaller scale flash-type games. Is that really a difference? I'm not even sure that's a valid characterization of the MMOs vs. VWs.
I really think the primary difference is one of focus. MMO's are primarily about the game, with the social aspects an important, but secondary aspect. VW's are meant to emulate the social aspects of the real work in a convenient virtual setting as their primary function. They include a game or games to facilitate the social aspects and provide something for less social players to do.
That's pretty slim. Perhaps the real answer is there is no big difference, other than that which the publishers choose to market and the fans choose to perceive. World of Warcraft is a Virtual World, but more than that it's also a MMORPG. There are RPG games in 2nd Life, but more than that, it's a Virtual World.
What do you think?