One of our earliest design goals with World of Warcraft was to ensure a healthy rivalry between the Alliance and the Horde. Cross-faction communication was banned outright, even where it made little or no sense in the lore. Entire realms are dedicated to PvP. Battlegrounds and quest hubs feature prominent Alliance and Horde iconography. We want to foster a sense of factional pride, a real identity with your brothers and sisters in arms.