I haven't bothered to review books on Amazon in the past. One of the biggest reasons is that in reading other people's reviews I often get cross when I think they've been totally whooshed by the author, and I'm afraid my review will be awful to read because it will just be a rant about other people's reviews. However now the kindle ap on my phone makes uninfected reviews quick and easy to do, since if you go right to the last page, you are invited to rate/review the book right there on your phone.
NOW however, I am sucked in, because other readers sometimes tick a box saying "was this review helpful to you? Yes/No". If you opt in, you get an automatic notice when other readers tell "you" that your review was "Helpful to them". Oh boy. Zam's karma system has my body totally primed for this kind of social feedback addiction.
In learning to manage and ameliorate my mental illness, I've been told a lot about current scientific theories about not only how huge a component the "Humans are Social Animals" is to ourselves, but even how Social Interactions (of a bazillion kinds) shape our personal brains every step of the way, and even how Evolution burned social interactions into the human, hominid and pre-hominid brains as part of our Survival mechanisms. Just like there is an Evolutionary explanation as to why an several inbred Survival mechanisms can be hi-jacked into a gambling addiction, I'm certain that there is a doctorate out there for someone who properly links Evolutionary mechanisms in with social media addictions.