Something Awful has a flat out hilarious (if somewhat long in the introduction) article on the nerd bias of wikipedia. The point isn’t to say that one article or another on Wikipedia has factual inaccuracies, but rather to show how much more attention certain topics get than others. They suggest opening up two somewhat related articles, where one appeals to the nerds and the other does not, and see how much longer and more complete the nerd-related entries are. Some of my favorites are below. If you want the quick results, just click on Lightsaber Combat and you’ll get the point (“The master practitioners of Form IV make extensive use of acrobatic maneuvers often thought physically impossible without the aid of the Force.”). People contribute to articles they care about. And Wikipedia’s community cares about light sabres, fantasy characters, video games and acne.
Update: check out wikigroaning, which shows the difference by numbers. No idea how they are trying to measure it, but its very funny.