The rapid growth of commercial sharing platforms such as Airbnb and Uber, the growing number of economic sectors affected, and conflicting interests among involved stakeholders have made the sharing economy a disputed topic full of (political) controversies and legal questions. Should sharing activities be monitored closely with strict regulations? Or should the invisible hand determine direction of the market? What exactly is the role of the government? What is going on in other cities? What can be done? This part provides information on the challenges and helps cities to rethink traditional regulation and policies and experiment with new approaches.