FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Advantages of Online Games
Some features of online games offer advantages to us as game developers, and some offer advantages to players, attracting people who might not otherwise play computer games.
Online games offer opportunities for social interaction. The social aspect enhances the players' enjoyment of the experience. Girls and women have traditionally shown less interest in interactive entertainment, especially games for personal computers, in part because these tend to offer solitary activity. Women represent a much greater proportion of the online game market than they do the single-player game market, partially because they enjoy interacting with others.
At the moment, most games offer only limited social interaction with conversation restricted to typing text (chatting), which is awkward while you are trying to play a fast-paced game, but more and more games include voice communication. When enough people get broadband access, online games could include video as well. A time might come when we see players dressing appropriately for their roles in the game so that they'll look cool on camera.
As the creator of such an online game, you're more than just a game designer; you must also be a social architect. This is actually your toughest challenge, far more difficult than designing the core mechanics of a single-player game. An online game isn't an experience that you lead a player through; it's a petri dish for growing social situations, and it's nearly impossible to predict in advance what will happen there.