The problem in my experience is not with wikipedia but with students using it. Instead of addressing these problems with a blanket ban by educators, why not put emphasis on teaching students the correct way to use wikipedia and the dangers of not doing so? On another note, a recent "other" niggle on misuse of wikipedia, I was shocked when someone complained about some seminar reading I had set the other day because there WASN'T a corresponding wikipedia article (which could be plagiarised) - clearly there is a problem when such a resource as wikipedia becomes so key to the way people are working (in this case, at a top UK university) that they find it much harder to work without it.