For a while now there has been a push against Wikipedia as a reputable source of information. Normally this is rationalized because Wikipedia is freely editable. However I trust Wikipedia precisely because it is freely editable. Of course, there’s a little more to it than just that.
Wikipedia’s freely editable nature if it were not tempered by its policies would indeed be a reason to distrust it as a source of valid information. However Wikipedia does have policies on how things should be edited. Chief amoung these is that anything put on Wikipedia must come from an outside, non-wiki source. Simply put, you think someone’s yanking your chain, check the sources! Even better, if they are and the sources don’t match edit the article to be what it should be.
It’s a concept that has been around for decades. Far longer than Wikipedia, Web 2.0, the Internet or even computers. It’s called Peer Review. Each of the articles are peer reviewed by hundreds if not thousands of people a day. Because of this articles will, over time, get more refined. The general quality of the articles will increase. Furthermore the complete history of every article is maintained. Every change back to the first entry on the page is there for all to see. Compare the 2001 version of the page on ASCII to the latest entry.
From time to time do articles get vandalized? Yes. But those vanzalisms are often caught quite quickly and corrected. Until they are one can check the history and often find a non-vandalized entry they can either reference directly, as I have above, or to which to revert to remove the vandalism.
Even so I take Wikipedia entries with some modicum of skepticism. But then, that is how people should take any new source of information. Check their sources, think through their logic to see if it really leads to the conclusions they draw. Generally speaking I have not found Wikipedia to be an overtly horrible source of initial information.