The CR releases that had problems with cracking have a metal post that the disc is pressed onto. The metal is not flexible enough and every time you put the disc into the case or take it out, it puts stress on the hole in the disc. Lots of people have reported radial cracks starting from the hole in their CR discs, and I'd really recommend either keeping the disc in an envelope inside the case (not on the metal post), or at least making a CDR backup that you keep somewhere safe.
Yep - all mine were ruined. I have backups on CDR, except for Biokenetics, which was too far gone to rip. Cool design, poor execution.