The exclusivity lasts for four months. Yeah it's hardball but it's not permanent, and it makes sense for them to make short term deals like that to boost the launch. I'm not sure how "bad for readers" it is, since it's available on pretty much every device that can run K4PC (and rooted Nooks). Bad for B&N, yeah.
Didn't Barnes and Noble just
get exclusive rights to the Peanuts comic collection for Nook Color? Did Amazon pull those books from sale?