Motivation crowding theory is an phenomena in economics that explains how, for example, paid labor can undermine intrinsic motivation. In particular, I am interested in the effect that crowding out has on free and open source software projects where large number of contributions may come from volunteers. Unintuitively, it seems that paying people to do a task may reduce the amount of work completed.
Web pages that discuss the topic include (and in particular its relevance to free software and other information commons):
- Wikipedia articles on the crowding out in economics theory and on Motivation crowding theory
- Page on the Rewards Controversy
- Discussion of the issue as it pertains to free software as it appeared on Luis Villa's blog
- Mako's article on Problems and Strategies in Financing Voluntary Free Software Projects
- User:Evan Prodromou's Paying wiki contributors
Enjolras, Bernard. 2002. “Does the Commercialization of Voluntary Organizations 'Crowd out' Voluntary Work?.” Annals of Public and Cooperative Economics 73:375-398. 
Frey, B. S., and L. Goette. 1999. “Does Pay Motivate Volunteers?.”.
Gneezy, Uri, and Aldo Rustichini. 2000. “Pay Enough or Don't Pay at All.” Quarterly Journal of Economics 115:791-810.