There was a recent thread on the ae list about backup and archiving. For a large organization like Primal Screen, it’s still really hard to beat tape backup for compact physical storage and cost per gigabyte, but for individuals it’s really common to use optical media for backup.
An equally common question is, “What media should I use?”. There are a ton of manufacturers, OEM’s, and generic media on spindles. Luckily, Patrick McFarland has done most of the research for you in his article How To Choose CD/DVD Archival Media. He gives a history of different flavors of optical media and recommendations on which flavor to use as well as specific manufacturers he recommends. Very useful stuff. Hopefully, he’ll take the time to breakdown his recommendations on Blu-ray and HD-DVD once the dust settles there.