MMO-Champion has released further information about Account-Wide Mounts, specifically which ones will not be account-wide. Some of these make sense: Paladin, Death Knight, and Warlock mounts as well as the new Jewelcrafting mounts that will be released in Pandaria will not be account-wide.
However, there are some that I’m a little disappointed about. Both the Grand Ice Mammoth and the Mekgineer’s Chopper will not be account-wide. This is also the case for the new Grand Expedition Yak which will come with your personal reforger.
Although I’m disappointed about these decisions, I understand the reasoning behind them. Blizzard doesn’t want everyone running around with these special mounts and if you want one on every toon of yours then you better be ready to spend A LOT of gold.
Keep checking in as I post more information about the upcoming acheivment changes in Mists of Pandaria!