Well, there's really no such thing. But you can make it work. In Server Admin, create a realm where you want your WebDAV home folders to be. Give Auth/Browse access only to an admin. Then just create something like /etc/httpd/sites/WebDavUsers.conf and add the following:

<Directory "/WebDAV/folder/username">
  <LimitExcept GET HEAD OPTIONS>
    require user  username
  </LimitExcept>
</Directory>

It seems that Digest authentication under OS X comes automagically from NetInfo which means we don't have to edit any password files.

Now only the admin can see all the home folders, but each user can connect to http://server/username and see only their home.