According to this article, a Dutch magazine did an extensive test of CD-R quality. Data was burned onto thirty different CDR brands, and a shocking number of them were unreadable twenty months later.
Backups are crucial. All of us have files that are too valuable to lose if the computer won’t start tomorrow – financial data, work files, e-mail, photos, music. But there’s no obvious “best” way to do backups – and CDRs may be more fragile than we realize for long-term archives.