This would also present a real issue with server population control.

Right now, all servers are equal in terms of what the core game offers. The only differences between any two given servers tends to be the number of people on it, and the things directly related to the number of people (pug raiding is easier on high pop servers, usually a better economy on high pop servers, etc). However, there is no "Server X is better for Horde because it controls 3 more zones than server Y does" for good reason. Once a server gets "good", people will want to move to it. The more people that try to move to it, the faster it hits capacity and the dreaded login queues begin.

On the flip side, "bad" servers would just get worse as people started a mass exodus away from them. Soon there could be 50 servers up, but only 5 that people actually want to play on while dozens are barren wastelands. After all, whats the incentive for the masses to spread out evenly across realms to help with Blizz's server load if there is active reason to not go to them?

Sure, some people would go just because its a blank slate they could mold, but most people wouldn't.

So yeah, I don't think we will ever see a time where you can just log into a random server and be able to tell which one you were on because of how different it was.