Why don't my users appear in the address book?
The main reason a user won't appear in the Address Book is because they don't meet the Address Book policy
of your site. The Address Book policy enables you to select the level of involvement a user must have to appear in and have access to your site's address book. For example you could set your address book policy so only current members will appear in the address book. For details on how to modify your address book policy read the address book user guide
Another reason that will stop a user appearing in the address book is if they don't have any address details entered. Only the users who have addresses entered will appear in the address book