This Wired Campus article is a few weeks old but it's worth pointing out. Martha Groom, an associate professor of interdisciplinary arts and sciences at the University of Washington at Bothell, required each of her students to write an article for their final project and submit it to Wikipedia.

All the papers met Ms. Groom's criteria. However, it turned out that some of them did not make the grade for a Wikipedia article. Admittedly, some were removed because they covered ground already present in Wikipedia. Yet others were removed because they did not meet Wikipedia's standards.

Another interesting point to note was that it was difficult for her students to find a topic which had not already been covered in Wikipedia, testament to its breath of coverage.

She also opines that even though there are nonsensical and inaccurate entries on Wikipedia, those that are in the know should be part of the process of improving those entries.

Ms. Groom's Wikipedia experiment aside, it is good to remind students that all encyclopedias are not primary sources. However, many good Wikipedia articles point to more authoritative sources, so it can a good starting point.