A year or so ago I bought a CD on eBay with a lot of scanned-in technical data. When I got it, I picked off the things I was going to need relatively soon and printed them off. All went well.

A couple of days ago I tried to load the CD and it wouldn't read. Tried it on several drives on different computers and different OS's -- same result.

I realize that it wouldn't take much, maybe a few bits melting away in the boot record or something, but I thought these things were immune from that for a lot longer than a year or two.