I can see the point of it. As the game matures and some of us realise we've been playing one game for more than four years, value-add starts to become a necessity.
And in the same way that friends come and go in RL, we move around in-game as interest takes us and as we make and say farewell to friends. I've had, in effect, a different main in every expansion, and two in vanilla. If I hadn't levelled a mage and druid of each faction I might be looking to turn my old night elf druid into a tauren.
If the WoW designers appreciate they've created not only a game but a social operating system of sorts, this kind of option gives people the option of following their friends across servers and factions as interest takes them. It's in keeping with some of their other changes, of gradually opening up content to people who stick to a guild out of friendship and loyalty rather than join a raid guild they maybe don't like so much. The e-peeners with their achievement titles(*) still get to swan around Dalaran in their shiney epics and on their special mounts. Meanwhile the rest of us get to eventually see the kind of patch content we never saw in vanilla WoW - or even Sunwell in the Burning Crusade.
Going to be one hell of a thing to achieve technically though.
I actually used the paid server transfer function recently for the first time. I wanted a disenchanter for my RP-server warlock.
(*) I still want the title Guardian of Cenarius!
