Grapevine became single source of authentication. Authentication denial became slow when groups became too nested. Added syntactic identifier for groups so that the authenticator could distinguish groups and expand only those. Also keep flattened groups for authentication purposes. Did not predict email usage well.
Experts are always remote.
Operators should not have to understand Grapevine internals. Have remote fsck capabilities. Special expert interface. System logs in regular text. Record all activities of a server.