When You Are Overly Dependent on One Product: Apple's "Problem"

The Wall Street Journal has a great chart today (shown here) that highlights how increasingly dependent Apple has become on the iPhone as the one product driving a substantial portion of revenue and profit.   Many analysts have expressed concern about this dependency.  I find it an interesting discussion.  On the one hand, it does appear worrisome to have so much of the company's fate reliant on one particular blockbuster product. On the other hand, a firm has to be careful how it responds to this type of "problem" that emerges with success.  Diversifying recklessly simply to reduce dependency on a single product can be a recipe for disaster...yet many firms have made that mistake when faced with this situation.  Moreover, we know that focus can be a powerful dimension of any strategy.  Jobs preached focus relentlessly during his time at Apple (and at Pixar).   Will a company lose focus if it tries "too hard" to reduce reliance on one hit product?  It's a delicate balancing act, and it will be interesting to see how Apple navigates this situation in the years to come.