I've long been a staunch defender of Wikipedia -- a site that I think many of us find quite useful. Most of the criticisms directed at Wikipedia come off as misguided -- and usually come from people who only just realized that anyone can edit it
and insist this is somehow bad
before recognizing that this usually tends to be pretty good, because it means mistakes tend not to last very long. That isn't to say that mistakes aren't made -- or even that they're not made quite frequently. But, as long as you recognize that Wikipedia, by itself, is not meant to be the definitive source, then it is still an amazingly useful repository of information that can be used as a starting point.
However, Simpson Garfinkel has an interesting article pointing out that there is one element of Wikipedia's relationship to "truth" that should be examined
. That is, the site very highly values verifiability over truth. In other words, it will always side with a citation over personal knowledge -- even if that citation is incorrect. This leads to some odd situations, when you think about it. After all, people will point out that Wikipedia's advantage over something like Britannica is that mistakes stay for much longer in Britannica. But, that might only be true if the Wikipedia entry isn't based on a false citation.
If the Wikipedia entry is based on a false citation, and there's no other citation that contradicts it, then it's likely that Wikipedia's entry will remain wrong, but citable. So, the easy editing of Wikipedia is a bit meaningless if the source of the false fact is not also editable (or if there's no citation that shows the original citation is wrong). I've seen this myself lately with the short entry about me. While I do take quite seriously the typical admonition not to edit your own entry, I have checked it at times. What amuses me, is that it tends to have my birthday wrong (flipping the month and the date, such that my real birthday -- December 8, or 12/08 -- is flipped to August 12, or 08/12). I've been watching a couple of people (one of whom I'm pretty sure I know) argue back and forth about the date, with the person who keeps flipping it back to the wrong date claiming at one point that he is me. He's not. Of course, I don't take this as evidence of Wikipedia's failure, but more a reminder of what the site is and what it's not. It's a useful starting point for investigation, which is quite often reliable and sufficient, but I wouldn't recommend betting your life on it. Or even your birthday.