The main problem is that since it is a community created encyclopedia, anyone can write an entry and anyone can go in and change the content of any entry. While this is an innovative approach to online collaboration and information sharing, how can you - as a researcher - know that what you are reading is accurate and reliable? Even Wikipedia acknowledges this problem; read their comments on researching with Wikipedia: http://en.wikipedia.org/wiki/Wikipedia:Researching_with_Wikipedia.
With no author names associated with any of the articles and no editors overseeing the quality of information, there is no way to determine the expertise or basis for why a person writes or edits an article. Maybe they are writing on a topic that has been a lifelong passion or maybe they simply want to see their words (or their 8th grade research assignment) published online for the world to read. Nice, but not academic.
For your academic studies, please don't rely on Wikipedia because of its easy access and convenience. When you're conducting research, your goal is to find the best information available, which does not always translate to the most convenient information. There are alternatives to Wikipedia. Britannica Online is one and more libraries are adding online subject encyclopedias to their collections. But again, since high quality information is your goal, sometimes a trip to the reference section of your library will yield the best results.
Here's an article on Wikipedia from MSNBC with some of the recent problems: http://www.msnbc.msn.com/id/17740041.
