Wikipedia is fast becoming the authoritative web site on almost everything. I believe there is a danger in this. The beauty of the Internet is that you can get data from a variety of sources. This allows you to decide for yourself on the subject you are researching and allows you to get many viewpoints. On technical subjects this allows you to gather more information and on non-technical subject it allows you to make up your own mind based on the pro and con viewpoints.
Using a single source such as Wikipedia not only cuts down the information you are exposed to but allows a biased viewpoint to be promoted. For example, I looked up the Wikipedia entry on an author who has loudly attacked the pharmaceutical industry. His Wikipedia entry makes him look like a criminal and the critique of his best known book was obviously written by someone who had never read it. Who controls the entries to that page? Clearly the pro-viewpoint on that author has not been given the chance to refute the con-viewpoint.
The academic field is now expressing the same doubts about Wikipedia: Cornell Profs Slam Use of Wikipedia
Another reason to be cautious of Wikipedia is a quality issue. How do you know the entry is accurate? While this can apply to a lot of other sites most of those other sites don't allow just ANYONE to edit them. Wikipedia does, and it takes no responsibility for the quality of that editing. Take this example: Wikipedia falsely reports Sinbad's death.
So next time you see Wikipedia appearing at or near the top of your search results think twice before clicking on the link. And if you do use Wikipedia make sure you also look at other sites to make sure the data you got is accurate and unbiased.