There may be sub-sections in your organization where it is more appropriate for people to have a seperate address book. This can best be done by making an Independent Group.
They are often used for activities which involve people from outside the organization such as the 'parents and toddlers' group and the softball league . As an independent group you can delegate people to maintain the contact information for this database only without giving them access to the full home database.
Independent groups also allow you to provide restricted access to your web site. Part of the registration process requires new applicants to indicate which areas of the web site they would like to register with. A member who is registered only with the "softball" independent group may not see articles, events and forums restricted to members of the organization and may only see contact details for other members of the "softball" group in the address book area.