The Internet Archive has announced a project to preserve physical copies of scanned books. There are two reasons for this. First, the original book is more authoritative than the scan. Second, books last longer than hard disks.
I find this interesting in the context of my Seventh Generation project. The letters I’m writing will be printed, but I’m planning to have electronic versions as well, hosted here at leppik.net. And I’m relying on the Internet Archive’s wayback machine to keep those available long since leppik.net has gone away.