tarsnap, the Unix-friendly backup "for the truly paranoid," has saved important files for me. I won't bore you with those details. I'm sure you can draw on your own memories of data loss. Instead, let me praise tarsnap's tremendous value. I'm using it to make two backups a day of my server's entire home directory: all my notes, all the configuration and data files for my TUI/CLI programs, and all my websites' files. (This works out to about 25 MB.) I store these backups for about three months.
How much is this costing me?
About 3.5 cents a month. At that rate, the 15 bucks left on my balance should last me another 35 years. (Of course, tarsnap charges based on usage, so you may have to spend more -- or less -- than me.)