Participation Inequality: Encouraging More Users to Contribute
http://www.useit.com/alertbox/participation_inequality.html

Nielsen, Jakob
Alertbox
2006

Abstract:

In most online communities, 90% of users are lurkers who never contribute, 9% of users contribute a little, and 1% of users account for almost all the action. Your website's design undoubtedly influences participation inequality for better or worse. Being aware of the problem is the first step to alleviating it, and finding ways to broaden participation will become even more important as the Web's social networking services continue to grow.