If they're forcing you to purchase a certain amount of books, and you don't, your hardware would most likely get turned off; meaning that you are really leasing it. Which is complete bullshit.
Err...I would expect that this wouldn't have been implemented this way. It most likely would have worked like Audible: a set monthly subscription fee, and you would get a set amount of "Kindle credits" to spend in the Kindle store every month.
Maybe that's one of the reasons they didn't go that route? The subsidized cell phone business model can suck for consumers (sorta the point Bezos was making), but requiring a minimum book purchase is still something some people might go for.
I have no idea how they'd implement it, but I suspect you'd pay a monthly fee that "earned" you X number of books. You'd hope they wouldn't let you "forget to buy enough" and thus lose your Kindle service.
