While I am a fan of this type of content, I don't believe it really has a place in WoW. Azeroth is a much more story-driven, linear experience than most people want to discuss, and Blizzard likes to hold our hands through it all to make sure we're doing things according to plan. I don't think that's a bad thing, just one approach to an MMO's leveling and group content. In games like City of Heroes, the player-created content that was available made sense in terms of logistics and volume. For WoW, I can't even fathom how hard it would be to separate the wheat from the chaff.