How to prevent the deletion of important groups

We almost missed this one.

In Domino 9 you can edit the Directory Profile to protect against accidental deletion of important groups.

Customizing the Directory Profile:

Open the Profile Document. People and Groups -> People -> Actions -> Edit Directory Profile.

Enter the names of groups that you want to prevent from accidental deletion in the Administrator client user interface or by AdminP. The list of protected groups defaults to LocalDomainAdmins, LocalDomainServers, and OtherDomainServers. You can remove the defaults and add other groups. Save and Close.

Note: This feature prevents accidental deletion of groups by a user of the Notes® client, the Domino Administrator client, or the Domino Web Administrator client. Is it not intended to prevent programmatic deletion of groups through C/C++/Java APIs.

Important: Whether or not you add any new protected groups, protection is initialized only when you save the customized directory profile.