jkOnTheRun's piece: Verizon Wireless jumping in the femtocell pool (http://www.jkontherun.com/2008/04/verizon-wireles.html) drew my attention to femtocells. These are small cellular "towers" for in home use, that send voice traffic over your existing broadband connection. Sprint's AIRAVE (http://www.sprintenterprise.com/airave/index.html) deployment, though limited, is further along than Verizon. This is mostly for voice, so AIRAVE probably does not work with the Kindle's WhisperNet. In any case, the obvious alternative would be to add WiFi to cell phones and (particularly) to data-centric devices like the Kindle.

I read somewhere that the Airave is 1xRTT enabled but not EV-DO enabled. I think this means it will work with the Kindle, right?

Yes, but there would still be the matter of the service agreement. The hardware isn't cheap. My understanding is the deployment model the carriers are looking at would involve a monthly fee to be able to either radically discount it or provide it for free. (They love monthly fees.) Since Whispernet users don't have a direct billing relationship with Sprint and the goal is to keep the connectivity cheap enough to roll into the price of your books, it's hard to see how this would fit in. I don't think most people would want to pay a monthly fee for Kindle connectivity in their house where they most likely do have other internet access.

I don't think most people would want to pay a monthly fee for Kindle connectivity in their house where they most likely do have other internet access.
True. How about this for a use case, though:
Your house is out-of-range for Sprint. I'm not that up on coverage areas, but I'd guess that there's a high probability that there's no good cellphone carrier for your home in this case. So, you get a Sprint Airave and get Sprint cellular service.

Now all you have to do is somehow register your Kindle for access through the Airave.