Yes, I know that Apple has 10% of its enterprise value in cash. I know the firm has no debt. But I also know that the company spends like crazy on R&D and sell-through is everything to a firm that is playing in this space. The problem with these sorts of firms is that when you’re running on afterburners it’s nearly impossible to pull back without losing control and crashing, simply because you’ve built a culture and corporate environment that is filled with “true believers” operating at a corporate level where everything has gone right — and thus you all believe it will continue to.
Amazon’s primary “lever” is the ability to play around the edge of the sales tax system. This gives it an instant 6% (on average) price advantage over everyone else, more than enough to offset the shipping costs (which you pay in any event; whether shipped directly to you or to a retail store, you still pay for it in the product price somehow.)
But that sales tax loophole is going to close. Over the next few years states will find a way, as the revenue shaft is getting out of hand for them.
Like Karl said, not a “crash coming tomorrow” kind of thing, but a future speculation. Tax loopholes such as the one that powers Amazon close. Unless there is some kind of majick lobby by Bezos, this is bound to happen as tax revenues further contract at the state level. The Apple thing is also simple. Markets dry up for stuff like this, though I do see the consumer public in many cases giving up on other necessities before their techno-baubles.