I thought I would comment on this because stumbling upon it was really a flashback to me.
Once upon a time, way back in the 90's, I and a friend of mine were waiting to enter an exam at the University. I don't remember now if it was Structure of Matter or Microelectronics. The fact is that we were speaking about how easily a CD-Rom got unreadable. Both of us had such an experience with properly stored CD-Rom and we were wondering about alternatives. The subject moved to the more general problem of storing information and finally we found ourselves talking about paper as a storage medium.
Many years later here's Jeff Atwood blogging about the same subject and introducing a software to get the job done.
Never did it myself, and I don't think I'm going to. I've got ZFS and snapshot-powered backups to protect my data. Nonetheless this flashback makes me wonder about alternative ways to store my GPG secret key to bring it with me...