Wikipedia is the only one solution to the social disease named ignorance. Here you can cure your lack of culture, and you can find out many things that you have never heard before. It's impressive the amount of information and knowledge that's available on this virtual encyclopedia. It's a massive archive of facts, dates, names, numbers, stories. And the simple users are the contributors of such material! It's very easy to contribute. Every page can be updated by everyone, if the material is object of controversy.
This means that if you a biological scientist and you find a page on some biological topic, you can debate the worth of what it has been written there. There's open space for debates and discussions, about the truth and the correct interpretations of everything.
Actually, I just wonder if this space for discussion can be considered as something of positive or negative. I give you an example: I was looking for information about Stalin. His page is full of infos, but there are many interrogative points. So, the result is: can we arrive to some truth, to some interpretation of historical facts that cannot be debated, and that we can accept withour conditions as the final and more realistic "truth"? History offers many cases similar to this ones.
By the way, Wikipedia is a very important tool for learning something more about the world and the cultures. As Marzio Valdambrini has claimed, it's a very important instrument of cultural democratization.