I'd pay for a "Kindle highlights & notes, for groups." I very often have the "everyone in my team must read this book" impulse, buy a bunch of copies, and then it's really hard to sync who's where, what they're finding interesting and to share notes.

The notes you take for yourself aren't the same ones you'd take for/with your team (imagine highlighting something and saying "see @jack, this has everything to do with what we were discussing on that project", it'd be awesome).