From the earliest days of development, we knew that we wanted to include some form of large-scale PvP combat in Guild Wars 2, but how would it work? We knew right away that we wanted three teams fighting against one another on a series of huge maps in the Mists (our world vs. world battleground) and that each team would be composed of an entire server full of players. Including three forces in world vs. world acts as an excellent balancing factor, preventing one team from growing too powerful and ruining the competitive balance of the game. Two teams can gang up to counter a more dominant third team, a dynamic that simply isn’t possible with only two opposing factions.
Welp, I think I'm sold.