I sometimes find myself defending Wikipedia to people. Usually their concern is about random people being able to add incorrect information. Although this is possible it is usually corrected quickly. My experience in using Wikipedia is that it is generally of very high quality and, if nothing else, gives me some good links to check out.
I usually begin my investigation of a new subject with Wikipedia. Sometimes even before Google. Depending on how important it is that I’m getting complete and accurate information for a given subject I will check out the references and possibly the discussion page.
The other day I was looking up Favicon on Wikipedia and was impressed to find that the W3C article “How to Add a Favicon to your Site” links to Wikipedia. What this means to me is that the Wikipedia Favicon article is of high enough quality that the W3C (the people that write the specs) links to it as an authoritative source of background and supporting information.