#7 - Nov. 2, 2012, 8:09 p.m.
As a matter of fact, now seems like a good time to follow-up with everyone with the latest information.
There's an item you can buy with a character that has reached (Revered, I think?) that will increase all reputation gains with your characters for the MoP factions, one for each faction.
Thank you for noting this, Malmström. In my original message, reaching Revered with any particular faction on Pandaria would have triggered double reputation for all characters on the Battle.net account with that same faction. After testing this internally, we felt the "trigger" wasn't obvious enough so we decided to create an item that players can purchase which, when used, grants the user's account with the bonus.
The changes to reputation gains are intended for Patch 5.1, but please do keep in mind that the patch is still in development. If there are any further changes, we'll let you know.