I noted the beginning to be different from the middle, in terms of the life-stages of a startup and the way in which it needs to operate. Is the end then also different from the middle? I think so, but at the end stage - you'd expect the company to be far beyond the startup stage.
Products such as Sony's Walkman and Sega's game consoles just did not see the disruption that was headed towards them. They did not change as the market changed, allowing rivals such as Apple and Sony/Microsoft/Nintendo to out-compete them on feature sets different from the norm - such as carrying all your music, all the time.
Some of today's leaders, Netflix and Google, show us the measures they are taking to prevent an 'end'. For example, Netflix was once a mail order DVD business. They anticipated the change that was coming and went to an online streaming model, cannibalizing their "bread and butter" business.
Google is more interesting. For over a decade they've had a search engine that has been their crown jewel. Changes to it have been subtle and incremental. Other ideas they've had, such as GMail or Google News, were boxed in different places - typically as 'Google labs projects'. With Google+, this has all changed.
Every part of Google's empire now seems to be an experiment. They have integrated Google+ across their product suite, and are tweaking it constantly until it works. Of course, what 'works' will change as the market changes, but the model they've adopted would seem to cope for that.