If you want to look at the downsides and limits of “market category thinking,” the slide rule category provides some excellent examples. Keuffel & Esser Corporation, a company founded in 1867 in Manhattan is a good place to start. In 1962, the company introduced it’s DECILON slide rule into the booming market for slide rules, and on the strength of this line was able to go public on NASDAQ in 1965. But by 1982, the firm was forced to declare chapter 11 bankruptcy. This same year, AZON corp buys ownership of K&E Trademarks and K&E is no more.