In a nearly unabated fashion, shares of Apple (AAPL) have continued to charge higher to new all-time levels following its blow-out fourth-quarter results.

Without question, it is the most-adored stock by investors and the darling of Wall Street. So, a roll of the eyes is the typical reaction when the rare pundit or analyst does come out with a negative opinion on AAPL. However, as we discuss here, there is a legitimate bearish argument, other than just "the stock has run too far, too fast."

Apple's fourth-quarter results were indeed astonishing. All of its primary products -- iPhones, iPads, and Macs -- easily outperformed expectations. In fact, during the fourth quarter, it became the world's largest smartphone maker, with roughly a 24% share. Looking ahead, the tech giant also has key launches in the pipeline, including the iPad 3 and the next version of the iPhone. There is little doubt that the company will continue to sell its devices at a mind-numbing pace, and that consumers will continue to line-up at its stores when the latest versions launch.

So, with that said, many are probably wondering how AAPL could possibly be a "sell." There are three primary issues that need to be considered. The first of which is less important, and is more of a short-term concern. The other two, however, could have longer-term ramifications for the company and the stock.

The first issue has to do with the euphoria that still envelops the company following its much-celebrated fourth-quarter results. It would be foolish to discount its phenomenal quarter, but there is a very important point to be made. A good portion of its sales come from vendors such as Verizon (VZ) and Sprint (S). In an effort to meet anticipated consumer-demand, Sprint in particular loaded up on iPhones to the point that it overstocked by a wide margin. In fact, the carrier spent about $20 billion on the devices and now holds a glut of inventory. Clearly, it will take several quarters just to work through this inventory, so investors shouldn’t expect a repeat purchase of that magnitude anytime soon.

The more pressing concerns, however, have broader implications for the company and its future. For instance, it is rather amazing that AAPL shares barely blinked following the passing of Steve Jobs -- the company's true visionary. Yes, Jobs left behind a road map for the company to follow, along with perhaps the "next big thing" (Apple TV), but the company cannot replace the image, and marketing genius that he emanated. He said it best himself: "I create products that people don’t even know they want." Is there anybody at Apple now who possesses that ability?

The truth is, Apple is a company that is completely consumer-driven, and consumers have flocked to it largely because of its brand identity. Jobs was the ultimate purveyor of this "cool" image. The problem now is that, with Jobs gone, the company loses that innovative mind and that absolutely crucial marketing talent, and the competitive environment is becoming more and more difficult. Google's (GOOG) Android operating system is capable of providing essentially the same functionality of an iPhone, and these devices are not as expensive.

Finally, there is the law of large numbers. It seems highly improbable that Apple can continue this rate of growth, especially given the increasing competition and the fact that emerging markets are slowing down. In a recent article, Gartner Research predicted that global smartphone sales volume will slow to 39% from the 58% we saw last year. Combine this with the probability that Apple won't be able to squeeze out much more in terms of margins, due to economies of scale being mostly played out, and the case can be made that AAPL is starting to look like a "sell" -- maybe even, dare I say, shortable.