A colleague and I taught a "Google and beyond" class recently, looking at advanced search techniques and other web tools. We included a bit on Web 2.0 (or some of it - I think I am too old for some of it) and mentioned Wikipedia.
So it was interesting to see this - http://news.independent.co.uk/world/americas/article2331980.ece - in today's Independent. Someone who has edited many entries on Wikipedia, who appeared to be a professor of religion, turns out to be a "twenty something" with no expertise in the area. He has been used as an expert in factual disputes at Wikipedia, and has been quoted as an expert by the New York Times.
I don't think that everyone who edits entries on Wikipedia is pretending to be someone they are not. I imagine many are knowledgeable enthusiasts for their subject. There was an article in the Times (or London) last weekend about some of the editors. I do wonder if particular subjects attract this sort of controversy, or the sort of tampering that has been talked about in various places, with people editing their own entries, or adding in scurrilous things to other people's. But it is an interesting phenomenon to talk about in our classes...
Here are links to two ResourceShelf posts about Wikipedia, one from 24 February and one from 7 March.
And here is a link to a Guardian story about a course at University of East Anglia (Norwich, UK) which assesses students on their editing articles for Wikipedia.