Wikipedia - the free encyclopedia that anyone can edit.... says a lot doesn't it!
Wikipedia is collaboratively written by anyone who wants to add their two cents worth about a particular subject. While articles may have been written by people in the know, there is a chance that not all information is accurate. When using Wikipedia as a research tool, users need to be sure of the validity of the information. This can be sought by viewing the source of the information and interpreting the accuracy of the author. Allowing anyone to edit and update information, makes Wikipedia susceptible to vandalism and unchecked information.
In the classroom I would still encourage my students to use Wikipedia as a research tool. I would, however, ensure that they are aware of the possibility of inaccurate information and make sure that they are checking for validity of their information.