Hello...(excuse my english)
I've been researching for a while this topic and I have found that actually what "eats" cd's is a fungus...yes...a fungus...they creep into the reflective layer from the outer border of the cd and sometines thru the polycarbonate layers. They use the aluminum as food . I live in the tropics (Panama) and 5 years ago lost a Von Karajanīs Bethovenīs 9 Symphony CD (put that one in the trash can)but recently I've found a MGI PhotoSuite SE installation CDROM with the same problem (I will keep this one this time). I do not recall the URL, but there is a couple of guys in Spain researching the exact nature of the damage done by this fungus.