I've seen several posts on this and even tho I understand the idea I have to disagree. Each of the server types are setup for a specific social environment. Server type populations are based on the overall popularity of that environment. You can make toons on any server so if the population level is low there it's due more to lack of interest than not being able to transfer. Crossing server type is fine but mixing them together would just create even MORE problems. I want transfers available as much as the next person but lets not go overboard. The creation of some grand master server is interesting but would create chaos.
I play PVE because I like the storylines, exploring, and NOT getting jumped by highlevel bored people who just like attacking those that stand no chance against them...remember, its not real pvp if you cant lose, its called rape! But I digress... The last thing I want to deal with is someone in RP mode telling me to get in character or even answering a page for a heroic in character on a PVE realm. I've seen it happen a few times, it got ugly...and I wasn't the one chewing them out for it. I'm not hating on the scene mind you but I don't enjoy it which is why I play on a PVE realm. This being just one possible situation of mixing different realm types.