How do the Internet and new interactive Web-based tools, for example, wikis and discussion boards, affect people and their behavior in organizations? This chapter will show the emergence of social structures in Internet-based systems over time. Based on results of an empirical investigation of an Internet-based knowledge-sharing system, the author demonstrates the change of roles, expectations, and activities in online communities. Finally, the author sketches some essential process criteria for introducing online communities, which are extended parts of organizations (e.g., companies and institutions), characterized by a large size and supplemented the formal company.