Ethan Zuckerman has posted some fascinating thoughts on emerging biases in the coverage of Wikipedia, and how best to address the issue:

Amazing though it is, Wikipedia is not flawless. It's got a problem common to almost all peer production projects: people work on what they want to work on. (This "problem" is probably the secret sauce that makes peer production projects work... which is what makes it such a difficult problem to tackle.) Most of the people who work on Wikipedia are white, male technocrats from the US and Europe. They're especially knowledgeable about certain subjects - technology, science fiction, libertarianism, life in the US/Europe - and tend to write about these subjects. As a result, the resource tends to be extremely deep on technical topics and shallow in other areas. Nigeria's brilliant author, Chinua Achebe gets a 1582 byte "stub" of an article, while the GSM mobile phone standard gets 16,500 bytes of main entry, with dozens of related articles.

He also points to the CROSSBOW ("Committee Regarding Overcoming Serious Systemic Bias On Wikipedia") Project, which is attempting to address some of these issues in a structural way. But I think Ethan's right that the real solution is to broaden the base of contributors -- in much the same way that the "blogosphere" has broadened in scope dramatically over the last two years, Wikipedia should also as it becomes a more widely discovered and appreciated resource. The Wikipedia team could bootstrap this process just by looking for subjects that are currently under-covered and doing outreach to potential authors, to bring Wikipedia to their attention and help them understand the benefits of participating.