"As we've already discussed, we’re 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. To prepare for this new service, we've removed the restriction that prevents players from creating both Horde and Alliance characters on a PvP realm."
Holy crap... I almost wished I was on a PVP server. Mostly since I just imagined the benefits of being able to flip to an alt and corpse camp someone annoying on your own faction. Of course if I started on a PVP realm I'd not have a horde alt near 80 unless I transferred it (something I'll probably never do unless it was free).
One step closer in breaking down the barriers between factions. Eventually I'd like to be able to chat with the opposite faction, have them show up on my friends list, and run instances with them! Ok we'll probably never get to run instances with the opposite faction so long a Blizzard can make money off faction transfers, but the communication thing doesn't seem as far fetched as it once did.
Cross faction communication would be most useful for PVE server guilds that have a sister guild on the opposite faction. It is not uncommon to have alts on the opposite faction just to do the quests and see the content specific to the opposite faction. Being able to still keep in touch with all your guildies no matter which side you happen to be logged in on would be a huge benefit to communication.
That being said I probably don't want the player I just pwnd to whine at me, but compared to gold spammers and idiots on my own faction that would be a non issue.
The ultimate solution would be cross faction guilds... where a single guild can contain players from either faction and they would be able to communicate with each other, but not to the opposite faction outside the guild. These types of things already exist in lore, such as the argent crusade, cenarion expedition, and many other in game "guilds" having members from both factions.