Dan mentioned it in a quick note earlier this morning, but this is such a big piece of news, to my mind, that it deserves an even bigger mention: in patch 2.3, Heroic badges will drop from bosses in Karazhan and Zul'Aman.
That's a gigantic change. We can only guess that it'll work the same way that Heroic instance bosses do now-- every member of the raid will get to grab their own Badge of Honor for each and every boss kill. And that is big-- currently, the badges are only available from bosses in Heroic mode dungeons, which means the only way to get them is to run Heroics.
Of course, whether Heroics or Karazhan are harder for you depends on your experience and your raid, but my sense of the general consensus is that most guilds are already farming Karazhan, while Heroics are only being run by small groups of really experienced players just to get the badges. And when you don't need to get the badges from Heroics any more, what reason is there to go in there?