Actually, the answer is right there in the story, and it's one word: iPhone.
> the iPhone accounted for 69 percent of its revenue
Without the iPhone, Apple would still be huge, but they'd just be a luxury computer maker who dabbled in some portables, and there would be no talk at all of having passed Microsoft.
That's the big challenge for Apple right there. It's a one trick pony, stock-wise, with an enormous valuation. It's not at all obvious where to go from there.
They need to diversify even more but that means either back to their computer roots, which would be devastating to the stock price, or find even greener pastures than one of the most commercially successful products on Earth.
