Blizzard talked about it before and today has gone live with the ability for users to change their Faction.

Blizzard employee posted the following on their message board:
” The new World of Warcraft Faction Change service is now live. As we mentioned previously, [ http://forums.worldofwarcraft.com/thread.html?topicId=18031079410&sid=1 ] we’ve been in the process of developing a new service for World of Warcraft that will allow players to change their faction from Alliance to Horde or Horde to Alliance for a fee. After purchasing a Faction Change for a character, a player can choose any race of the opposite faction that is compatible with the character’s class. For more information on the Faction Change service, please read the FAQ, [ http://us.blizzard.com/support/article.xml?locale=en_US&tag=FCFAQ ] or visit the Faction Change page [ https://www.worldofwarcraft.com/account/faction-change-intro.html ] to get started.

Based on further community feedback, we have also decided to offer a race change service in the future. Players who choose to switch races will be able to change their race within their same faction and class. Additional details will be released at a future date. ”

Responses so far seem very positive and players seem more anxious for the ability to change race in a future update.