Facebook's Manipulation of Users' News Feed

Have you been seeing a lot of joyful stories of your friends on your Facebook news feed recently? Or, are you tired of reading upsetting news on Facebook which causes you to be sad throughout the day? Maybe the reason is that you have been selected as a participant of Facebook's news feed manipulation study. Yaay!? Check this article to see how Facebook manipulated its users' news feed to create emotional response. Well, although it is interesting to see the results, should Facebook manipulate what we see on our news feed at all? What does this study tell about Facebook or other Internet giants being able to do to people with the data they have? I wonder what you all think about it.