1. Player wants to defect to faction X.

2. Player does a series of quests to defect, and becomes hated with their original faction and only slightly less hated or unfriendly with their new faction.

2b. Or, player would be hated with both and become a "neutral" or an "exile". (On a PvP server, they'd be open to attack from any faction. All zones would be contested for them. They would only have access to the neutral cities, AH, etc.)

3. Player does quests to build faction with their new choice. Break into cities, steal stuff, kill people, etc etc. 4. Player becomes Neutral with their new faction and can now interact and play just as any normal person would of that faction.

5. ???

6. Profit

Before joining either the Alliance or the Horde, one must be a devoted, loyal, and honorable person. Having a character turn their back to this would betray everything they swore to protect. With the high tension that already exists between the two factions, a characterÂ’s safety could not be guaranteed in any location as people on both sides would be very unforgiving.

You are free to roll new characters at anytime if you want to play the other faction, but we have no plans at this time to add a feature that changes an existing characterÂ’s faction.

Via WoW Forums