http://en.wikipedia.org/wiki/Muqtada_al-Sadr
is my own favorite example, and also the site of one of my extremely rare personal ventures into editing.
There was a time when this article was heavily slanted in an anti-US fashion. The important tidbit is that the article went significantly beyond all mainstream sources in claiming that the U.S. broke the truce agreement. In fact, all mainstream sources were very vague on that point; there seems to be little information about what the truce agreement actually consisted of, and little information about how the fighting started again.
However, my experience in helping on the article was quite good, but of course people may pay me more deference than I would otherwise deserve on the merits of my writing. My sense of it, though, and I do a *lot* of reading on talk pages and edit histories of controversial pages, is that the majority of contributors are willing to work with others to find a way to ensure that we don't make claims that go beyond the best available evidence.
(I have not read the current version of the article.)
--Jimbo