Could you imagine the level of annoyance in WoW if you had to travel to Outworld every time you had wanted to do dungeons? I am personally happy they plan to implement in this way.
And guess what, it wasn't annoying at all, jump on the flight point, grab a drink, jump into the dungeon, and IF you needed waiting, talk to your group members, set up some tactics, tell jokes, make friends (this was THE way to recruit new people before LFG ruined everything)! Finding people on the realm was much easier (you ended up having quite a few on your friends list that you knew were nice), avoiding annoying (euphemism here) people was also easier, in fact, the real *****s tended to leave the server fast because soon nobody would group with them or even want them in their guild.
I knew most of the active people on my realm.
Then came Wrath of the Lich King with it's cross realm dungeon finder.
Net results (some of them anyway):
- Nearly no talking in groups, no jokes, no stupid pulls "for kicks". Just rushing through content, the faster, the better. If people said "hi" at the start "bye" at the end you had a seriously social group.
- Ninjas ran rampant. Before LFG ninjaing meant that in no time you would not be getting any groups at all on that realm for a seriously long time. Now it just means getting booted from one group so you can start over with the next...
- Frustration of ending up in a bad group and the way people dealt with said groups (badly and often rudely), see also next point.
- Easier to quit and find an overgeared group than actually try to do the dungeon with the people you've got. Being a "quitter" earned you seriously bad rep back in the day, now it's standard procedure.
- Total lack of support for newbies, back in TBC people mentored newbies, took time to explain the tactics etc, nowadays they're seen as ballast and often kicked because "they suck" or because people just can't be bothered with even the most basic explanation of a bossfight.
- It heavily devaluated the rewards from dungeons. In TBC finding a group for MgT and actually completing it was a feat for most people, not to mention getting some of the neat loot from there. Now a dungeon is just a way to gain "dungeon points".
- It mostly killed the social aspect of the game outside of your own guild.
Also after Wrath hit (or more correctly, when ICC was released) I moved realms, I raided there for like 6months. By the end of those ~six months when I decided to quit raiding I realized I knew NOBODY (no, I'm not being dramatic, literally NOBODY) on the realm even though I'm a fanatic "dungeoneer" and often pugged raids (even though I had no real reason to, being in one of the top guilds in the realm) and wasn't averse to PVP-ing either (though I despise arena).
No, I'm STRONGLY (to put it mildly, basically it's something I'd quit playing over) opposed to any form of cross-realm LFG.
EDIT: edited for lots of typos...