If you are interested in reading about how and why powerful incumbent firms fail to define their industry, the article on Marketing Myopia by Levitt is a good one. First published in 1960, it still holds relevance today and here is one written almost 15 years later as a review. But you can see its relevance even today–VOIP changing cable companies to being Content/Internet providers, PC Games changing the landscape leading to and Interactive Entertainment industry instead of Video game, movie, plays etc, and medical devices and drugs converging to form the Life sciences industry instead of the pharmaceutical, device, biologic industries.

http://www.casadogalo.com/marketingmyopia.pdf