Popular vote getters are Un'Goro (which gets my vote with those damn dirty raptors plus being so far away from Alliance cities), Azshara and Swamp of Sorrows. Even a blue threw in his two cents. CM Drysc's vote went to Shimmering Flats. Great to look at, not much to do. In fact, that seems to be the theme of most of the complaints about zones: visually appealing, but lacks significant content.
What about you? What do you consider the worst zone in the game? And why?