Since you are reviewing notifications - what about our audience, our readers.....Newsletters are a gun shot approach to gaining an audience. Since I write on a wide range of subjects, it would be GREAT for the reader to sign up IF I add more photos, more links... For example, my home improvement Hubs, I try to add photos as I find them. If someone is seeking ideas for a sun room and wants more photos, it would great if the reader could be notified. Also, the comments on some of the Hubs are fascinating and a great learning tool. Most importantly, this mechanism could drive more traffic.