Why don't you edit that Wikipedia article?

A question that I’ve been thinking about for sometime and that leads on from something I asked in this question here.

I’m just wondering. You see an article, you know it’s down right wrong and incorrect, and have sources elsewhere of correct information. Besides limitations due to time, why don’t people edit the articles (the whole idea behind Wikipedia) to ensure that the articles are actually correct and people are getting the correct information?

You wouldn’t accept an incorrect answer on Fluther, you would point out the problem and correct it, therefore improving the knowledge of both the person who asked the question and the person who answered it incorrectly (and possibly others who read the answer). So why not do the same on Wikipedia and improve the quality of information that is provided by this free, community editable encyclopedia?