Facebook user emotional contagion research

A research study into the effects of so-called 'emotion contagion' conducted by Facebook, the University of California and Cornell University on a swathe of Facebook users has been described as 'creepy', 'manipulative', and 'unethical'. 

Conducted over a one-week period in 2012, the research, which detected that very small changes in the emotional state of our environment can have knock-on effects for how people behave on on social networks, saw the content of news feeds changed for a random sample of 689,003 Facebook users, with one group experiencing positive content, and another experiencing only negative content.

However, it transpired that the researchers had failed to gain the informed consent of the sample, leading to a heated debate on the nature of academic and corporate ethics boards and Institutional Review Boards, and on the nature of Facebook's relationship with its users.