Hello,
For any achievementwhore out there that is still working on The Exalted, there's a way for you to save yourself some days (or even hours, depending on which faction you missed) getting this achievement.
It's kind of simple really, and most of you maybe could've guessed it. But here goes:
If you are Exalted with The Horde Expedition (The Alliance Vanguard if you are Alliance, respectively), and switch factions, three out of the four of these reputations will be transferred to your new character and be automatically put at exalted. You still have to grind your fourth one back from neutral to exalted though.
But good news everyone, because this whole ordeal is an extremely easy way to add an extra exalted reputation to your collection, because if you transfer, there won't be a -1 to your total exalted reputations.
Proof that this works:
Link to two armory sites, on which you can see that a character has 38/40 of "The Exalted" in progress, with only 37 reputations on exalted.
The World of Warcraft Armory - Omgmewmewcat @ Stormrage - Achievements
The World of Warcraft Armory - Omgmewmewcat @ Stormrage - Reputation
Happy achievementwhoring.