Blizzard is rolling out an interesting new feature in the beta test for World of Warcraft: Mists of Pandaria. The new cross-realm functionality will allow players from different realms to play alongside each other in lower population zones.
"For many years now, the significant majority of the player population online at any given time has consisted mostly of characters at or near the level cap," explained Blizzard. "This has resulted in an environment where characters that are leveling up experience a world that has fewer other players to interact with than what the world was designed for. Cross-realm zones give us the capability to ensure that level-up zones retain a population size that feels more like the high level areas of the game, leading to a more fun play experience for characters of all levels."
When you enter a zone designated as "cross-realm," you'll be able to see players from a select group of different realms and form groups with them. You can also group with Real ID friends in these zones. Trade will be restricted, though, to ensure no one "games" the server economies. Capital cities and auction houses will not be merged in any way.
This same technology also allows Blizzard to reduce overpopulation. They can split a realm's zone into multiple copies. This should make questing easier in the new Pandaren starting area or the high-level zones introduced in the expansion, both of which will be extremely crowded on launch.
These new features target a major issue that affects many MMO's: player density. An overcrowded zone makes it too hard to complete quests, while too few players means you can't find anyone to help you with group adventures. It doesn't matter how good an MMO's content is if the player population doesn't accomodate it. These new additions to the game won't solve all the problems on that front - for example, a low population server will still struggle to field successful raids - but it's a big step in that direction.
Pandaria has been in beta since earlier this year. It's expected to launch by the end of 2012.