One of the problems of high market share is that it can bring in high operating costs. So if you are churning 50 billion of whatever currency a fixed overhead of say 20 billion is rather less important. Should the churn-over drop, can the fixed overhead also show the same flexibility? In apple's case it probably does not make a whole difference since the margin is so high they would have time to adjust to falling markets. Financial markets hate uncertainty so they wobble as soon as look at you. So the marketplace for certain things is showing signs of being finite. Those who want them in the main have them. Those like me who are still wanting to know what the fuss was about still cannot find where the magic is hidden. Many of us would still be happy to settle for ten seconds of apple's cash flow, but we will see how the market evolution pans out.
The end of the world is certainly not due.