Currently, a log on the Client is useless, because it does not save the information from the "Client console" (status bar) in log.nsf.
In the setting of the Client ("File -> Preferences...") there Log Settings, which has a tick "Enable Logging". Set it, but it does not affect on the ...
User Activity in Database properties show access of users to your database. In mail, sometimes on would like to know, WHICH document somebody else read.
Even if you do not grant access to everybody, Full access Admins can read your mail.
I could imagine a $AccessedBy field similar to ...