One of the most important expectations to set early on is about involvement in the process. Many project stakeholders accustomed to traditional-style development view their role in a software development project as akin to dropping a car off for service: You tell someone what you need done and come back at appointed time to pick up the finished work. Stakeholders, especially anyone in a product owner role, will need to understand that this is not the right way to build software-intensive products.
Source: “Succeeding with Agile”, Mike Cohn, Addison-Wesley