Sharing Economy (SE) systems use technologies to provide individuals with information that enables the optimization of resources through the mutualization of excess capacity in goods and services; thus, SE systems contribute to the reuse phase of the Circular Economy. In this paper, we assess existing SE services and identify their weaknesses in areas that are not technically connected to their core functionality, but are essential in creating trust: information security, personal data protection and economic incentives. We then propose to take a systematic approach to non-functional requirements specification, where a well-defined, structured approach would pay immediate dividends. As existing frameworks are not holistic and have several shortcomings, we set forward a research agenda, both for ourselves and the community, aiming at systematizing the specification of non-functional requirements for SE services in a top-down-top manner.