Anything on this list:
http://www.wowinterface.com/list.php?skinnerid=28751
In particular, I see unathorized "fan updates" of Titan Factions pop up fairly frequently, and the ancient original version from Corgi can be removed as well, as I took it over (with his permission) years ago. I'm actually not sure why that version is still on WoWUI, as when I took over the addon I had ownership of the project transferred to me. It seems to have reappeared at some point since I removed all of my addons from WoWUI about a year ago.
As to why I stopped hosting my addons on WoWUI, keeping up with comments, bug reports, feature requests, and updating on three different sites was just too much. Since WoWUI was by far the least usable site (the dim greenish color scheme, tiny font sizes, and extremely cramped layout on the update page made it difficult and uncomfortable to use with visual impairments) and had the lowest download counts, it was the logical choice to cut.