How to make user directory private?

Currently, anyone can see everyone on the server. Is it possible to restrict user directory to only those who are in the user’s contact list? If a user has a username of other user, he can add him to his contact list and then communicate. Think of skype for an example.

You can restrict the search on nicknames only, default is also to search for usernames and e-mail.

One of RC’s strength is that it does NOT copy your addressbook. A manual contact list is also not available and is not necessary, as it would be congruent to the list of private conversation channels.

It depends on the use case. Doesn’t it? I do not want everyone to see everyone on the list. I just want to hide it. However, If you have a username, you can easily search and add that person to your contact list and start conversation. Is it that difficult to implement?

I am sure you understood what I am trying to achieve here.