doh! i missed this in the march 30th PTR patch notes. i must have been too excited about the united nations achievement fix. lol.
"Many "Account Bound" heirlooms are now labeled as "Battle.net Account Bound", meaning that they can also be traded or mailed to characters that are on different World of Warcraft accounts under the same Battle.net account."what will this mean for pet collectors? some pets that were previously bound to account will change to bind on battle.net, making it more convenient for players to mail and learn a few of the rarer pets on multiple accounts under the same battle.net account.
the list of battle.net bound pets isn't very long at the moment. a user from twitter took a screenshot showing which ones changed and compared "BoA" to "BoBattle.net".
note: unless proven otherwise, this change does not seem to indicate that pets will be mailable to characters on different servers on a single account. to transfer companions between servers on an account, players will probably still need to pay to move one toon (holding the BoA items) to another server.
something else that's interesting to note is that the crawling claw is no longer bind on account on the PTR. it's possible that with patch 4.1, this archaeology pet will turn into a bind on pick up pet.