Many MMOs allow players to choose sides or affinities. Sometimes, like in City of Heroes/Villains, players can choose between a clearly good or evil side. In other games, like World of Warcraft, the good/evil divide is a little less clear cut. Of course, these choices don¡¯t always revolve around good and evil. For example, they may involve choosing a race, or choosing between technology and nature.

For example, let¡¯s start with the good and evil split. The graph below shows both an age and gender difference. Younger players prefer to be on the evil side, and this tendency decreases as age increases. There is also a relatively more mild gender difference in the mid-ranges where male players are more likely to be on the evil side than female players. What¡¯s interesting here is that the distribution roughly matches the 2:1 Alliance-to-Horde ratio in WoW.

Via The Demographics of Game Choices