Good find. It's hard to tell if they've held to that, though. The post was back from September. Given Blizzard's general thrust at trying to avoid previous mistakes (I gather that most people consider DAoC's exclusive divisions a mistake, and that was for a game that was designed with the divisions in mind for the capture the flag game.) so there's a good chance things like that might change. We'll have to wait and find out I guess.
I also found some other things on
www.worldofwar.net that say much the same thing as what Sprig found. The Reputation thing might allow someone to switch over to a different faction over time even if they keep the group-exclusive division in. Who knows? Here's what I found:
Neither faction can party with members of the other faction or enter each others towns {unless in stealth somehow}. Reputation is said to help characters of the other faction to mix but how this is to be implemented hasn't been elaborated on yet. They can not understand each others language {Common & Orcish} unless in possession of language skills or ride each others mounts {unless masters of the Riding skill} or hire their flying mounts.
The Reputation interface has never been seen and not much has been released about it. We do know however that it will affect how NPCs and certain Monsters react to you and it is in some way connection to your faction alignment {Alliance or Horde}. The NPCs is easy enough to see as there will be NPCs of all races so it's only natural they'll be more accommodating to those of their own faction. Monsters, on the other hand, is an interesting slant on this and it'll be very interesting to see how Blizzard balances this.
"Non-player characters - such as quest givers and vendors will respond accordingly [to Faction alignment]. " - Blizzard Nov. '03
"Some things that a character’s reputation will help decide are whether certain quests are accessible and whether or not certain non-faction groups will attack on sight." - Blizzard Nov. '03