If a relationship is defined as the interaction of two people; how would a company track all the numerous relationships between perhaps a single person at a company and the various staff members within the servicing firm.
So John Smith works for ABC Corporation and ABC Corporation purchases services from PSI. PSI has 5 technical people who at any given time work with John Smith.
You want to document these relationships and perhaps unique notes from each PSI tech, but you also want want historical flow for John Smith.
This can be done with the opening and closing of activities and you can also use the Relationship feature of Dynamics CRM to build the relationship table.