It's really more effective to have a very regular backup (e.g. ".snapshot" directories are really nice), because you can't control all the ways a file may be de

It's really more effective to have a very regular backup (e.g. ".snapshot" directories are really nice), because you can't control all the ways a file may be deleted. Just because you protect one "rm" command doesn't mean there isn't another. Someone might have used unlink() in a Perl script or a C program. Maybe "mv" was used to write one file over another, or "cat >! filename", or a dozen other things. In the end, if a file needs to be safe then it needs a backup (and the sooner it can be restored, the better). And then given a good backup the file still needs an appropriate Unix group, owner, file access control list, etc. to minimize the chance that you'll ever need the backup.