Facebook Experiment – It’s You!

Facebook conducted a psychological experiment on nearly 700,000 users on the social network, although they didn't tell them about it -- until now.
During one week in 2012, the site's data scientists tried to prompt users to post either more positive or more negative comments by omitting words associated with positive or negative feelings from the new feeds of 689,003 users.
The research was published in the March issue of the Proceedings of the National Academy of Sciences, but has only started gaining media attention recently and Facebook users are not amused to learn that they were used as human guinea pigs.
The Animalnewyork.com blog wrote in a post, "What many of us feared is already a reality: Facebook is using us as lab rats, and not just to figure out which ads we'll respond to but actually change our emotions."
Source: The Wall Street Journal