In an intranet project this summer I modified the new-user registration scripts so that new users would automatically be members of the intranet (it was an intranet machine behind a firewall; I didn't want to manually add all the users to the authorized and employees groups). Apart from adding them to authorized_users and employess I noticed that they must also be added to the im_employee_info table, else the user info edit page would crash (with the "nsdb select statement didn't return any rows" error in the log). You don't need to add all the fields in the table, "insert into im_employee_info (user_id) values ($new_user_id)" will do fine. Christi: the url is /intranet/users/info-update.tcl.
You cannot edit the information of someone else, unless you know their password or click the 'become this user' link in the user admin pages.