One business type I can see this making sense for is food trucks, as I don't see amazon going into that business anytime soon if ever. Beyond that I tend to agree with you that giving amazon even more data seems like a horrible idea.
Although why anyone would buy their decorative paper from the back of a van is beyond me.
This makes sense for more than just Foodtrucks. The pain of fees is a very real thing for retail startups and if amazon is also going to give us a terminal that can take the place of a $3k+ POS system, then I'd be seriously considering it.