As I was browsing a few blogs this morning, I came across this post talking about what a ghost town Ironforge has become since the release of the Burning Crusade.
And really, it's not just the old world. Even Hellfire Penninsula has seen a major population drop. Gone are those exciting, chaotic first few days as everyone poured through the portal and unleashed their pent-up aggression on the unsuspecting demons and orcs of the land. There was an almost visible aura of energy and excitement in the zone. Now it's reduced to just a small, scattered population, and the initial flood of players has mostly outleveled the zone and spread out amongst the rest of the Outlands.
And as for Azeroth, the high-level zones are just eerily empty. I spent some time in the Eastern Plaguelands and Silithus recently, and I saw a total of one other character in each zone!
This, IMO, is one of the biggest flaws with a level-based game... the level-based segregation that comes with it. Especially when you organize your adventuring areas along level lines as well. This is a major community-breaking 'feature' that is only exacerbated by the expansion of the level cap.
I'm hoping that the next MMO I play isn't so divided and that I have a chance to hangout, adventure and have fun with new characters as well as old.