Starting a commandline like

    rsync -va -R files... host:/

and pressing <tab> changes the last parameter to "/"; the only
indication is a short blink as the commandline gets shorter,
but if you miss that and press <enter> (as the next completion will show
the expected /etc etc ;) you copy the file to the wrong machine - which
can be fatal if you copy files out of a chroot from another
architecture, and/or copy files from home directories in a backup.