Many online communities are emerging that, like Wikipedia, bring people together to build community-maintained artifacts of lasting value (CALVs). What is the nature of people's participation in building these repositories? What are their motives? In what ways is their behavior destructive instead of constructive? Motivating people to contribute is a key problem because the quantity and quality of contributions ultimately determine a CALV's value. We pose three related research questions: 1) How does intelligent task routing--matching people with work--affect the quantity of contributions? 2) How does reviewing contributions before accepting them affect the quality of contributions? 3) How do recommender systems affect the evolution of a shared tagging vocabulary among the contributors? We will explore these questions in the context of existing CALVs, including Wikipedia, Facebook, and MovieLens.