Interesting article from New York Times
The Age of Undoing
Facebook, for instance, allows you to register approval for a posted message in a very concrete way, by clicking a thumbs-up like button. Toggling off the button results in unliking your previously liked item. Note that this is different from disliking something, since unliking simply returns you to a neutral state. This kind of instant reversibility is now an inescapable facet of our digitized life — like it or un-.