Ever since word got out that Facebook had briefly manipulated some users' News Feeds to see how their feelings changed, a number of questions have popped up: just why did the company feel compelled to experiment in the first place? How noticeable was it? And was it worth the effort? As of today, we have some answers to those riddles. Study co-author Adam Kramer explains that Facebook was worried people would stop visiting the social network if they saw too many emotional updates -- a lot of negative posts could scare some people off, while a surge of positive vibes would leave others feeling left out. That's not what happened, however, and Kramer stresses that the company "never [meant] to upset anyone."