As a follow-up to previous posts on Wikipedia I'd like to recommend an article by Matthew Shapiro on Education Week called Embracing Wikipedia. He is also concerned about teachers banning the use of Wikipedia as a reference and refers to a recent study (Internet encyclopedias go head to head, Nature) showing that for every four errors found on Wikipedia you can find three errors in Encyclopedia Britannica.
That will no doubt come as a shock to many Wikipedia opponents but it's worth thinking about how reliable the traditional reference works actually are. Another point is that the Wikipedia errors get corrected, often very quickly, whereas the errors in the print encyclopedia don't get corrected till the next edition. This doesn't mean that Wikipedia is completely trustworthy, just that it should simply be brushed aside. It is one of many sources and since it is the sixth most accessed resource on the web it should not be ignored.