Well, Zips and Jazzs are similar and though generally rock solid, they are but glorified floppies and are subject to the same things that can corrupt a floppy easily.
Now that said, I have all my SFC1, EAW, OP, and 3 stuff all on Zips (100 and 250 MB units) and then backed up by CDROMs. Neither method is foolproof or corruption-proof. Depending on the quality of the CDROMs you buy, there is a "shelf life" to them. The inks and dyes used to make the digital patterns in them vary in quality depending by whom and when they were manufactured. Some of the lower quality ones will suffer some data degradation in shorter time. Zips, Jazzs are essentially magnetic and stray magnetic and electric fields can degrade them. Once, a friend put a floppy he just used to record some data in his shirt pocket; when he used it less than a half hour later, it was somehow damaged enough that all data was lost.
You might laugh at me, but stuff that is I consider important is redundantly backed up: on my HD, on a flash drive, a Zip disk, AND a 3.5" floppy (shoot, I'd do a 5.25" one if anyone still made those drives!). Since I normally only buy CD-Rs (not RWs), I use CD backup only when a particular set of files, say my SFC model collection, for argument's sake, reaches "critical mass", i.e., just a little under the capacity of a CDROM (600-750 MB).