It strikes me that this is a move in the direction of -- instead of having DRM-free books available for any device, there will be Amazon DRM-ed books readable on any device (except other competing ereaders). So, no need to worry about netbooks, tablets, etc. - one store can serve all. And if/when the Mac version comes out, the future Apple tablet/ereader can just become an Apple tablet that runs Kindle software.
For the non-tech buyers, why buy a new ereader with a new DRM to deal with? Just load the Kindle reading software on your current devices. A brilliant follow-up to freeing the ereader from the PC for buying/downloading books. Now you can read the Kindle books you already own on most/all of your devices. No tech expertise needed.
Bezos seems to be following Gates' path to monopoly: put your software on everything, or make it run on everything, and let consumers buy their way into your kingdom.