Ultrix' /etc/crontab as a time-bomb [short joke].

Hihi, our little training in risk-assessment tonight is the following sippet of a crontab entry, scheduled to run dayly around midnight: (cd /usr/preserve ; find . -mtime +7 -a -exec rm -f {} \;) why is this a bad idea and what happened to me last night as I was playing with my VAX6460? Answer: the /usr/preserve was a symlink to /usr/var/preserve which didn't exist. What happened next? All files that were not accessed for more than 7 days were being deleted (and I basically installed this system 3 days ago but had fast forwarded my system time from 1976 to 2002 the day before. :-)