An excellent discussion on Inside Higher Ed on the potential and pitfalls of Wikipedia.
Note to students: Professors look askance at papers that rely heavily on Wikipedia. Why? An anecdote may suffice. Last semester in PG 250 I had the students edit the article on social capital, which was the subject of the course. I told them they could make whatever changes they wished. I saw this as both a way to teach them about the trustworthiness of Wikipedia and also an experiment in "virtual trust"--would my students intentionally mess up an online entry that others rely on?
The answer: yes, they would. Several students deliberately posted observations about social capital that were patently false, while others cited themselves as authorities. And while most of these entries were later corrected by others, several are still there.
Many hands make light, but often unpredictable, work.