Wikipedia is a vast web site created by anyone and everyone. The nature of a wiki allows users to contribute, edit and delete information posted by others.

The problem with Wikipedia is not in the content; it's in the way that the content is created. The authors may or may not be experts in their field. Even if they are experts it is possible for a novice to edit an entry and remove key facts in order to generate controversy.

When an valid research site accepts an article from a source they do so knowing that the author has a vested interest in creating an accurate document. Their reputation (and maybe their income!) is on the line. As added protection a quality source will have review each article for authenticity.

Wikipedia relies on the public to handle these tasks. The result is source that is varied in the quality and authenticity of its information.

Can You Trust Wikipedia? : http://technology.guardian.co.uk/opinion/story/0,16541,1599325,00.html

Wikipedia vs. Brittanica: http://www.nature.com/nature/journal/v438/n7070/full/438900a.html