Abstract
In our increasingly specialized and professionalized service sectors, the days of dedicated continuing contact between a single provider and his/her clients has become a distant memory. Service provision in domains such as medical, legal, or financial arenas has become multilevel and multiplex, involving many layers of providers and their systems. Moreover, in contexts entailing long-term relations, such as cancer care, the participants enter and exit over time, varying in their identities, interests, relative salience, and influence as the stage of disease progresses.