Purpose of sync, adm, uucp, operator system users

[pindakoe]

Mandriva's default /etc/passwd and /etc/group list users and groups for various system users. The reason for some is obvious from their name (squid for the suid proxy; postfix to run the postfix mail-system, etc), but I wonder about the need for the following users: adm, sync, operator, uucp, news, games. None of them own files. Anybody who can explain these users and whether they can be deleted from the system?

 

The same applies to groups news, games. Surprisingly the group uucp owns some ttys in /dev/tty (I always thought uucp was the uold unix-to-unix-copy mail transfer system).