CD-RW
  Because change is an actual physical process
    Disk will fatigue and fail with extended changes < 100,
      some newer discs claim change up to 1000 times.

  Also, often CD-RW are readable only on CD-RW drives.
    The reflectivity of the cdrw disk is less than that of a cdr and 
      the older CDR drives were not sensative enough to read.

    In some cases, accessable only on the drive it was written.
 
  In 2002, a new protocol was finalized that standardized the CD-RW
    So that CD-R and CD-RW drives manufactured after that should be
    able to read CD-RW disk.