The only restaurant I can think of that I'd never go back to is Whispering Canyon Cafe; at least, not for dinner. I might try breakfast.
Oh, add the Garden Grille, in the Land pavilion. For the same reason as WCC- that skillet of overcooked, drab food. Yuck.
I will say that WCC had a great chocolate milkshake. Maybe I"d go and just get that.
The only way a list like this is useful is if you see the same restaurant mentioned over and over again (anyone looking forward to trying Planet Hollywood?) Then, compare with a list of people's favorite restaurants. If it's not showing up there, and it's repeatedly mentioned as a least favorite, then the choice is obvious.
Some restaurants, though, like Coral Reef, San Angel Inn, a couple others, will show up alot on both kinds of lists, because people's expectations are so different.
You should never discount a restaurant because you see one or two people complain about it.