Anyway, the point is: bless their invasive little hearts, but this was doomed from the start. People don't get sad because their Facebook friends are sad. We get sad because our Facebook "friends" are happy.
This is not me being cynical – of course I'm capable of empathy for the people I care about, and vice versa. No, this is a matter of Facebook not understanding its own product. For the average Facebook user, only a fraction of our "friends" are actually people we love – people whose setbacks strike us near to the heart, people whose triumphs uplift us along with them. The rest are former co-workers, friends of friends from that party that one time, people who were jerks to us in high school but not big enough jerks to reject their friend requests, and exes. Screwthose guys.
I realize that scientific progress sometimes means performing rigorous research on questions that seem self-evident. (I also realize that thisresearch is supposed to be done on people who know they're participating in a research investigation; never mind that right now.) But you don't need a study, informed or not, to tell you that the connection between our emotions and those of people around us are a lot more complicated than "sad=sad". All you need to do is look at a happy Facebook pic from your ex's wedding.
The study in question, published in the Proceedings of the National Academy of Science, reports that, for a week in January 2012, some Facebook users saw an altered timeline wherein posts with either "negative" or "positive" words got suppressed. A lot of the hand-wringing horror over this unauthorized experiment stems from the reality that users who were exposed to more negative content responded by making more negative posts, which implies that they were more sad. In other words, they were materially harmed by their experience as social-science abductees.
But the study doesn't seem to control for the possibility that people simply match their tone and word choice to that of their peers, to avoid being the tall poppy. In the end, it's not clear that Facebook found out anything about emotional contagion. It sounds more like semantic contagion to me.
If Facebook really wanted to make people experience unhappiness, suppressing "positive words" isn't going to do the trick. Emotions are way more complicated than the mere words we use, and it's not always posts with negative words that make us sad.
For its next mad-scientist foray into emotional manipulation, Facebook and Co should instead try building a news feed where users see only the following:
Notifications of career success from an acquaintance who is in the same field as you, but younger
Mushy "Happy anniversary, baby!" notes from your ex's new significant other
Cute snapshots of your friends' young child who they say is doing so well since they opted not to get him vaccinated
Triumphant posts of celebration from people who root for a different team/candidate than you
Memes involving a photo of a beach or flower overlaid with encouraging platitudes with at least two obvious typos
Off-the-chart FitBit stats
Profile pictures making it clear that the mean, gorgeous queen bee from high school is still – against any reasonable expectation of biology or justice – extremely gorgeous
Birth announcements from dear friends who gave their offspring really stupid names
I doubt there would be a "negative word" among them, but I guarantee you the emotional contagion would be off the charts.