Personalization of services often has to cope with the conflicting goals of allowing cooperation and sharing, which require common data formats and services, and supporting individual use cases, which require as much personalization as possible. In this paper we present the ShaRef approach to personalization and sharing, which on the one hand allows users to cooperatively work with bibliographic references, and on the other hand supports the usage of this information in personalized and diverse ways. The goal of this approach is to foster as much cooperation as possible, while simultaneously supporting users with individualized ways of reusing the cooperatively managed data. This way of building applications combines the beneficial aspects of information sharing and personalization. Using this approach, applications are better suited to become building blocks in information infrastructures that are built by users in unpredictable ways.