stated slightly differently....
In instances(MonoX CMS installations) where the "Groups" functionality is fully utilized, it would be useful to have some way of automatically adding users to groups.
Method option #1) Just like there is <add key="DefaultUserRoles"/>, if there was a <add key="DefaultUserGroups"/> newly registered users would automatically be included in specified content Groups, without having to go through the process to join them.
Alternate Method option #2) A different way of achieving the same goal would be to have the ability to add Roles to Group membership, just as you currently add users. result: If you could add the "Users" Role to membership of a particular Group, then all new users that register would automatically be included in the specified Group.