Amazon's foray into mobile is "just" a natural extension of their retail business. The primary purpose of the Kindle and their variety of mobile apps/services is to get consumers to buy digital goods from Amazon; just as Amazon (the retail) is to get consumers to buy physical goods. The logistics plays a large role in keeping the physical goods flowing; AWS gives them a solid platform to keep the digital goods flowing.
But the interesting thing is, I think, how Amazon realised that building a superior delivery network for bits would be just as much of an advantage as having a superior delivery mechanism for atoms was. You buy a kindle from them. Amazon ship it to you. You turn it on, buy things, and the bits just arrive. And Amazon have that process down better than anybody, even Apple.
