Just because it's region wide, it's not that different...
In EU during WoD we basically knew all good Ashran raid leaders by class-name-server. Faction was of no use thanks to mercenary mode and people were hoping from one side to another all the time
One could predict the outcome of the game by knowing opposing team leader's name.
And there isn't that many PvPers in general, we never were a big group anyways, so if you play regularly you end up knowing many names. I occasionally add people to my friend list this way.
P.S. I'm the Horde bastard