Wikipedia is not a credible source due to the fact that the information you're viewing might be either biased or inaccurate, or downright false. You gotta give them credit, it does make sense.
Pfft. On the proper topics, Wikipedia has a lower rate of errors than the Encyclopedia Britannica. If you want information on a popular book, a pop-culture figure, a movie, etc, there is no better place (though it still pays to look through the history to make sure you aren't victim of a recent vandalism attempt, though most instances of vandalism get corrected in less than 10 seconds, on average). The problem comes when it is a topic that no one cares about. Look at the history page and the discussion page and see how many different people participate on that page. If it doesn't look like many people care, then the probability of false information skyrockets.
One just has to keep in mind that Wikipedia is an encyclopedia. It can introduce you to a topic and help you formulate a framework for understanding other sources, and sometimes that is enough. It is a good first step in the research process. And a horrible last step.
Unfortunately, academia frowns on Wikipedia not because of the value of the content, rather it is because the perceived value of the contributors (aka, the unwashed masses). The common public has not jumped through the same hoops that most in academia have, so therefore academia does not want to listen to them and will spurn them.
A shame, really, since places like Wikipedia are incredibly similar to how print culture developed and the Enlightenment got started.
