Just before the release of WotLK Blizzard introduced the new achievement system. One of the achievements requires you to acquire 50 mounts, for which you are rewarded an albino drake mount. At the time it was fairly difficult to get to 50 mounts and required you to grind up Netherwing and Kurenai rep in order to meet that requirement. Now of course it's much easier with the plethora of new mounts released in WotLK. And so I finally completed this last night on my DK.