Ever since Wikipedia became popular there has been an ongoing debate as to how accurate a resource it actually is. Personally I'm of the opinion that it is a useful jumping off point for more serious research but should never be used as a trusted source of information. For this reason it should never appear in the references section of an academic piece of work -- a fact I find it hard to get students to take on board.
If you want a good example of why Wikipedia shouldn't be trusted, and why you should always consult the original sources where possible, I've just blogged about the inaccuracies in just one small piece of one article. If the rest of Wikipedia is as bad then we really are in trouble.