I think it's time Blizzard gave out free server transfers and faction changes as part of it's subscription. I think the service should be one free faction change or server transfer per toon per year. If you wished to do either more often then you would pay.
Here's the main reasons I think this should be done:
1. The game is almost ten years old. People should not be expected to be stuck on the same servers forever unless they pay or re roll. Things change and people should be able to move to other servers more freely.
2. Dead servers. There is many many dead servers, there is no way a player could know or expect a server they play on would go dead. It's not there fault it has done so and this would give them the chance to escape the dead server. World of Warcraft is a mmo and on many of it's servers it's feeling less and less like that and more and more like a bad single player game.
3. Broken factions. There is servers where you have a near 100 to 1 faction balance. No one should be expected to pay to leave that. It's not a lot of fun to play on a server where your faction is out numbered in a huge manner.
4. People would come back to play. There is a decent amount of people that have left the game due to the fact either the server they play on is dead or the faction they belong to is dead. If you gave those people a chance to come back and play on a server that was better suited to them, they would take it and subs would increase.
I know people will point out that this would cause servers to go further dead or for the mega servers to grow even more beyond where they are, let me address both.
For the servers going more dead, yes that's true but if you were to do this, the only people that would remain on them would be the people that wanted to play on such a server.
Blizzard could limit the options of servers people could transfer to, to prevent more problems with the mega servers and to help prevent any other server from becoming to large as well.