Blizzard will introduce cross-realm zones into the Mists of Pandaria beta. This will allow players to meet up and group with others in under populated areas of the world such as low level zones or areas which have been out-leveled by higher-level players. Cross-realm will allow players to form a group with others from “within a select pool of realms” in order to quest while the social structures of players’ home realms will remain intact. Capitals, the Auction Houses, and other high-population areas won’t be joined. You can view the FAQ on cross-realm zones here.