From the patch notes:
http://www.worldofwarcraft.com/patchnotes/
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Blacksmithing/Leatherworking specialization has changed with specialization providing recipes to make powerful items that only you can wear. You can now unlearn a blacksmithing or leatherworking specialization and learn a different one by finding the appropriate NPC, paying the fee to unlearn your old specialization, and then find the new specialist to learn a new one. Also, all of the old blacksmithing/leatherworking recipes that required specialization no longer require it and can be learned by any blacksmith/leatherworker.
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