Web services are an emerging technology to implement and integrate business processes within and across enterprises. Service-orientation can be used to decompose complex systems into loosely coupled software components that may run remotely. However, the distributed nature of services complicates the design and analysis of service-oriented systems that support end-to-end business processes. Fortunately, services leave trails in so-called event logs and recent breakthroughs in process mining research make it possible to discover, analyze, and improve business processes based on such logs. Recently, the Task Force on Process Mining released the Process Mining Manifesto. This manifesto is supported by 53 organizations and 77 process mining experts contributed to it. The active participation from end-users, tool vendors, consultants, analysts, and researchers illustrate the growing significance of process mining as a bridge between data mining and business process modeling. In this paper, we focus on the opportunities and challenges for service mining, i.e., applying process mining techniques to services. We discuss the guiding principles and challenges listed in the Process Mining Manifesto and also highlight challenges specific for service-orientated systems.