There are other ways for a file to end up unusable as well.
The best way to reduce loss of data is to take backups and
of course know where the backups are.
http://www.mvps.org/dmcritchie/excel/backup.htm
If you are running a business and don't have backups, you
automatically fail your audit. There is no valid excuse for
not having backups. Hardware can fail. Software can fail.
User handling and/or mistakes can destroy data.
Another way of losing data is to access removeable media
directly from Excel rather than from the harddrive. The worst
offenders was diskette drives and zip drives. But even though
CD and DVD drives are much more reliable you still should only
allow Excel to update files on your hard drive or on a network drive.