Ok, I admit that I used the word "iPhone" in the title to seek attention, but it is true. My first experiences with Stanza were on my iPhone. A friend suggested that I download the application. Free download. I often asked, "what is the business model?" Selling the technology is one possibility. The creators of Stanza have made a lot of money on an iPhone application. See release.
More seriously, it is an interesting play for Amazon. Heavy users of a service/function on a portable device – whether a PND, MP3 player, etc. – lean towards buying dedicated devices. I have a Kindle, and I love it. I have the Kindle application on my iPhone, but I don't use it. Casual users of these services will buy and use devices that are multi-purpose. Moreover, users don't want to worry about file formats. Lexcycle fills in some of these gaps.
Content players need distribution, content strategies and business models that span the range of portable devices. Adoption outside of laptops and cell phones is limited today, but devices such as portable media players, netbooks, etc. are filling in the space in-between.
Mobile strategies extend beyond a cell phone presence – more so for media companies today than those in other industries.