Looking at this idea, I can't find a single thing about it that strikes me as positive. Let's put my concerns into an example... Let's say you're a roleplayer. Not too unlikely, right? Okay. Now, let's say you'd like to play with people who happen to share this passion with you. Now what? How are, for the sake of this example, roleplayers going to find each other? They are rare enough as it is, at least in most modern MMORPG's, but a Mega-Server is just going to drown them in other players, whilst being unable to play the way they'd like to.
How do you think issues like this will be resolved? Do you think the developers even care about something like this?