According to Joystiq, one of their brethren has already "dinged 70" -- just 28 hours after the Burning Crusade expansion launched. The French player, Gullerbone, used the help of his guild Millenium to bastardize the milestone. By tap-leveling (where a player attacks several mobs and once he has the "tap" other players kill the character, with the instigating player getting the experience yielded) through various zones in the Outlands, Gullerbone (a mage) maxed reached the level cap. In an interview with World of Raids, Gullerbone thanked his guildmates and explained some of the process of leveling to 70.
