How to stop grouped users from seeing all users?

Question

I have several users organized into groups, and would like to make is so that users can't see people outside of their group (or groups). No matter how I tweak permissions, all users get to see every other user no matter what group they're in.
That is unacceptable and makes Server pretty useless when we need to protect the ID of our users. How can I make it so that users see only the other users in their group?
Thanks in advance!

Answer 1

Replying to my own query as it may help other noobsters.
I've been able to control which users and groups can see a project by using the following schema:
Create Project Wikis by creating a group with the project name, giving the group a shared folder and creating a group Wiki. Edit Access to Services and check only those services needed by the project. For example, check File Sharing and FTP for Wiki and FTP service.
Create People categories by creating a group with the name of that group of people. For example, you could organize people by firm or department or staff category. Do not create a shared folder or group Wiki. Edit Access to Services and uncheck all services. The people groups will acquire the services and permissions they need from the Projects they join as members.
Create users and require them to log in. Make sure "administer this computer" is unchecked and the Home Folder: drop down reads "None - Services Only." Edit Access to Services and uncheck all services. Users will acquire the services and permissions they need from the Groups they join as members.
Now, add users to the people groups as appropriate. For example, add all engineers to the Engineers Group. Next add people groups to project groups as appropriate. For example, the Engineers Group may be added to the Bridge Project Group as well as the Building Project Group.
Once you have users in your groups of people and groups of people in your project groups you can start the Wiki then point to it with your favorite browser. Sign in with the same username you used to create the Wikis. Select a Project Wiki then click on the gear in the upper right corner. Choose "Wiki Settings..." from the drop down menu.
In the Wiki Settings dialog that appears, click on "Permissions" in the left pane. Enter the name of the Project (Group) then set its permissions to "Read &Write." Change the permissions for "All logged in users" and "All unauthorized users" to "None." Save changes.
Now sign in as a user with limited permissions and verify that they can see only those wikis they're supposed to see.
On the FTP side, they'll be able to see all group folders but they can only open those they have access to. Not great, but better than a kick in the head.