Well here's a counterpoint view:
It has a lot of charts and modeling that I don't understand, but at a high-level view, this analyst pins the lack of profitability to Amazon's revenues growing in less profitable business ventures while growing relatively slower in the more profitable business lines. In 2002, 78.8% of revenues were from Media, 19% EGM, and 2.2% Other. In 2014, it's 29.6% Media, 64.8% EGM, and 5.5% Other. Media has much bigger profit margins than EGM(electronics and general merchandise), and the company's weight has shifted heavily behind EGM. AWS has good profit margins, and will grow quickly as it's a relatively new and blossoming business arm, but it's unlikely to grow to the kind of size that would shift Amazon's sales mix away from EGM. Under this guy's reasoning, this means we can expect Amazon's profit margins to continue to bump along the bottom tied to the low margins on EGM, and can't foreseeably create the kind of high margins on EGM that would justify it's high share price, since it's an extremely price sensitive business. It makes this stock questionable in the long-term.
Nevertheless, I still bought shares today because it's a 10% discount off of one earnings report that doesn't show some kind of underlying catastrophe. They'll probably rebound to some degree within a year. And hey, I don't have that author's powers of analysis, but maybe Amazon's shotgun strategy of trying to find new ways to grow their business will find a winner (This latest phone isn't going to be it, but maybe something else will be).