*Some products may require other firms to produce [[Complementary goods]], in order for the product to be useful. For example, a new format for storing movies (such as [[blu-ray]], or [[DVD]]), is unlikely to be successful without a significant number of movies being available in that format. | *Some products may require other firms to produce [[Complementary goods]], in order for the product to be useful. For example, a new format for storing movies (such as [[blu-ray]], or [[DVD]]), is unlikely to be successful without a significant number of movies being available in that format. |