I am also shocked by the reliability of CDs. I understand that the laser focuses past the scratches, and that CD media has redundant areas, but you would think that even the slightest scratch should refract enough light to cause the data to be read incorrectly. After all, each microscopic pit is either a 1, or a 0 (on a CD). 8 pits make a byte, or a single letter. Innumerable things can go wrong PC program using incorrect data. Anyway, label-side damage almost always destroys data. A caddy would be indispensable.
(How would an error-correcting algorithm work with holographic data?)