Kurt D. Bollacker on Avoiding a Digital Dark Age -- "Data longevity depends on both the storage medium and the ability to decipher the information":
... [In] the 1980s I was in high school making backups of the hard drive of my PC onto 5-¼-inch floppy disks. I thought that because digital copies were “perfect,” and I could make perfect copies of perfect copies, I couldn’t lose my data, except by accident. I continued to believe that until years later in college, when I tried to restore my backup of 70 floppy disks onto a new PC. To my dismay, I discovered that I had lost the floppy disk containing the backup program itself, and thus could not restore my data. Some investigation revealed that the company that made the software had long since gone out of business. Requests on electronic bulletin board systems and searches on Usenet turned up nothing useful. Although all of the data on them may have survived, my disks were useless because of the proprietary encoding scheme used by my backup program.
The Dead Sea scrolls, made out of still-readable parchment and papyrus, are believed to have been created more than 2,000 years ago. Yet my barely 10-year-old digital floppy disks were essentially lost. I was furious! How had the shiny new world of digital data, which I had been taught was so superior to the old “analog” world, failed me? I wondered: Had I had simply misplaced my faith, or was I missing something?