The problem turned out to be a faulty LED in the tape drive, which meant it didn't stop winding at the end of the tape. This fault would have broken my last tape if I had been unwise enough to put it in the drive. However, many modern tape cartridges are built more robustly. Problems with physical security . This affects all kinds of backup including tape, RAID and any other system where the data is located on one site.
Many people think of fire or flood as being the main risk, but the risk from crime is much greater.
We know one web business which was adverseley affected when someone stole their servers and all the backup systems and media. That's also a good argument for using a rackmount server . If your servers are screwed firmly into lockable cabinets, chances are they'll still be there long after yoru desktop PC's have disappeared into a waiting truck. It's also a good case for a redundant portable server . If you discover one morning that your main server has been stolen, the portable can help get your business restarted.