I think it's good to simplify group roles to two types.  But I think that we also need to allow administrators to take away privileges from members.  I can imagine a situation where administrators get paranoid over who joins their group and edits their groups bulletin board or starts to spam their group with irrelevant or too many messages.

As an alternative solution, perhaps an administrator can view on the group's home page a list of new members, followed by buttons or checkboxes below the member's name deciding the privileges they should have.  It's the way yahoo does it.

Administrators could also decide for themselves whether or not they want all new members to automatically have all the editor privileges, or be notified first of the new users.

As an administrator of a group, you can change the privilege of other group members to "Editor", by placing your cursor over the member's picture, clicking the "Edit" link, and then clicking the Privilege tab.

Giving the privilege of "Editor" allows that member to:

1. Message everyone in the group (Go to Admin Tools)
2. Post and Edit the Group Bulletin Board!
3. Remove Group content