Even before writable mini disks, the 8-centimeter in diameter small CDs and DVDs (a.k.a Pocket-CD), became available/affordable, I really liked that small form-factor. Today you find mini disks included with some computer accessories, used as a cheap way to include drivers and other software. Some video cameras use writable mini DVDs for content recording. However, I don't think those small silver optical disk became very popular ever and the rise of the slot loading drives surely didn't help.

It used to be that only on Apple computers one would predominately find slot loading optical drives (CD and DVD drives) while on PCs the less expansive but often faster tray loading drives were used. Generally, slot loading drives seem to be more convenient and offer a very clean look but are also more prone to jamming; most importantly however, slot loading drives don't accept 3" mini DVDs or Pocket CDs and Apple warns about using those.

Warning: The optical drive in your Mac mini supports standard circular 12 cm discs. Irregularly shaped discs or discs smaller than 12 cm are not supported. Noncircular or small discs may become lodged in the drive.