In WotLK you should find that things are a little more vigorous than what you are used to now. Many cities and settlements are constantly threatened and attacked by enemy hordes and monsters. For an example you will find that Valgarde in Howling Fjord is under a constant Vrykul invasion, and that Warsong Hold in Borean Tundra is under siege by the Nerubians.

In both cases you will see the Alliance and Horde forces fighting to push back the enemy invaders, and players who choose to actively take part of these battles will have a chance to be nicely rewarded with quest items that will drop from some of the elite mobs that will be a part of the battles from time to time.