The success of any product involves meeting expectations—those of the ultimate customer, those of management stakeholders, and those of the project team itself. While delivering something useful to the customer remains paramount, keeping all the participants informed and involved is critical to success.
If we want products that deliver outstanding customer value, then we must have a customer-developer partnership, one with responsibilities and accountability on both sides (and similar relationships with key suppliers). Agile teams constantly seek customer involvement and are always asking the question, "Is what we are doing useful to you in meeting your business goals?"