This is why we need fair use personal copies of DVDs, Jack:

If you think your prized collection of DVD movies will last a lifetime, think again - some are already starting to rot while others are falling apart.

Unofficial estimates put the number of affected discs at between one and 10 per cent. Yet some of the largest distributors for Hollywood Studios are accused of refusing to accept the problem exists and replace faulty products.

Last year Australians spent $398 million buying 13.3 million DVD movie titles - a three-fold increase on the 4.3 million sold in 2001, according to research firm GFK.

The technology, sold as a replacement for VHS video tape, with added interactive content, is now five years old and the DVD industry claims it is the most successful packaged media in consumer electronics history.

The failures are a combination of corrosion - known as "DVD rot" - and delamination, where the layers of the disc separate.

....Mr Byrnes has studied five cases of DVD rot - four in his own collection - and suspects the microscopic corrosion spots on the aluminium layer inside the disc could be caused by a "chemical attack", possibly related to the glue used.

One DVD website lists 18 titles known to have at least one bad batch, among them Planet of the Apes (1968), Men in Black: Collectors Edition, Independence Day and the Alien Legacy box set. [Sydney Morning Herald]

Let's see, if it's a manufacturing defect (your fault, Jack) that might not show up until the 90-day warranty period is up, it seems to me this would necessitate a backup copy.