This document discusses user-generated content in virtual worlds. It explores what motivates users to create content, and how developers can support creativity. It analyzes different types of user contributions like commentary, creation, and public actions. It also examines lessons from early virtual worlds like Habitat and different approaches taken by later worlds like Ultima Online and Second Life. It concludes that current virtual worlds don't fully harness the potential for social and goal-oriented user-generated content, and that "non-social" game types have leveraged publicly beneficial content more effectively.