I've addressed the issue of Wikipedia several times in recent posts as have others. Karim R. Lakhani and Andrew P. McAfee (Harvard Business School) have just written a case on Wikipedia that they are sharing free with other faculty. It would make for an interesting discussion with your students in class. As Professor Lakhani notes:
[The case] is "designed to have a “managerial” decision point - which forces students to choose between several alternatives and come prepared to class to discuss their rationale for their choices. A case discussion is typically 80 minutes long with the goal of having the students engage in discussion with each other and the professor to develop a particular point of view about the case facts. In a case discussion, “there are no RIGHT answers - but there are WRONG answers!” My role as a professor is to make sure that the main teaching points in the case come out via the discussion with the students."
What a great way to discuss the legitimacy of Wikipedia with your students while deciding what guidance to give them in using this source.
Thanks to Marcy Carrel (University of South Florida-St Petersburg) for directing me to this site.