This isn't exactly true. A vigilant user will run normal backups, and those backups will not be in a location that is writeable by the unprivileged user. In this way, it will not be possible for you (or an attacker) to completely wipe out your important files, only those changes from the last hour or so.
Based on an rsync-backup article that I bookmarked a long time ago (http://www.mikerubel.org/computers/rsync_snapshots/), I run backups of my important files (/home/, /etc/, /usr/local/, some directories in /var/, and so on) every hour to a /backups/ directory that is only writeable by root. Every day, I copy a backup over to another machine using the same rsync process.
Based on an rsync-backup article that I bookmarked a long time ago (http://www.mikerubel.org/computers/rsync_snapshots/), I run backups of my important files (/home/, /etc/, /usr/local/, some directories in /var/, and so on) every hour to a /backups/ directory that is only writeable by root. Every day, I copy a backup over to another machine using the same rsync process.