From my
experience on Wikipedia, unsourced articles are very unreliable
and may have plenty of wrong facts. Most of thse wrong facts are not
added due to malice (though that is not uncommon), but they were
added by people either from their (inevitable unreliable) memories,
from blogs and forums, which, on average have an awful lack of
accuracy or they are simply misinterpretations.
From my experience with Wikipedia, unsourced articles are generally
very accurate and moderately precise. When I find them in areas for
which I'm familiar with the body of knowledge and reliable sources, I
will spend time to go find the appropriate citations and sources as
time allows, to "back up" the already existing content with
appropriate references.
"Accurate" and "reliable" are not synonymous. Just because the
article
happens to have everything right does not make it reliable, because
there is no way for you to know that it has everything right.