A DVD shattered inside my DVD Drive how does this happen?

Sometimes a DVD or CD will shatter inside a drive due to the stress of the CD/DVD disc. If there are a lot of scratches or deep marks on the disc or on the inside ring where the disc locks in to spin occasionally there will be small fractures located there. When the disc is loaded and the drive spins up the stress from the lateral load put on the disc is to much and the disc will break (or shatter if the scratches or fractures are significant enough). Most new drives of today spin discs around about 2000 RPM and the newer Blu-ray or HD-DVD drives go upwards of that. Hope this helps.