I think the best thing we can do about this is to let our voice be heard I wouldn't call and do it or email it needs to be public like their
Nook Facebook page and
Twitter pages. Make sure you let them know they've lost you as a customer. If some media could carry the story the better as they did this quietly without warning.
I've been thinking about this. If this was some other store it wouldn't matter but this is B&N not some small ebook store. It's always been Kindle vs Nook. If we let them get away with this then more stores could follow this pattern to where you will be left with app or device reading only.
Right now you can sideload but I am sure this is only a step before they fix it to where you no longer can.