Connected Reams?

So I was doing my usual run to get fur from WoD to make into Hexweave Bags (still easier to make than future bags, something Garrisons ARE good for) and had some alliance shadowpriest running around also trying to farm. And what ensued was the usual “be a prick denial” tactics. Didn’t matter to me, only needed 35 and between the mounted zone special and the fast respawn rate it was easier to snag a wolf or two running and DoT’ing.

But he was here from Uldum, and I thought it odd because I didn’t think Bonechewer was connected to Uldum. Quick search here revealed that technically it is but it’s not? I mean Bonechewer is in a connected cluster with Aegwynn, Daggerspine, Gurubashi and Hakkar, but Uldum is only clustered with Antonidas. So what gives?

Did Blizzard connect more realms into clusters and not say anything? Is it sort of all one big mega-cluster now? Or did the implementation of War-mode do something to it?

There are realms that share an auction house, and can mail/trade between all characters on those realms, such as Antonidas/Uldum, and others.

Otherwise you can also see other realm characters in different zones especially older content. I believe these happen somewhat dynamically depending on how many are logged in, and server loads. You can talk, interact and group up with the other characters, but you cannot do any trades. Main cities are the same way.

I forgot the technical name for it, but they implemented it back in WotLK so that lightly populated zones would merge with random other realms so the zones would present more folks to interact with. I remember it was WotLK since I used to camp out for the Time Lost Proto Drake and you had the slightest of chance to find it before the tech. And after the tech, you can camp out with tons of other folks looking for it. Never did get that mount…