Facebook emotional contagion experiment controversy

In mid-2014 a story broke about Facebook conducting psychological experiments on the newsfeed of almost 700,000 of its users without consent or IRB approval. The aim of the research was to test the hypothesis that users would experience emotional contagion – that is, if they perceived others as posting more negatively they would post more negatively, and if they perceived others as posting more positively they would post more positively. They tested this by manipulating the newsfeed users saw showing them either more negative posts from their friends or more positive ones. The effect was significant, albeit small; altered newsfeeds demonstrated a slight emotional contagion effect. This kind of A/B testing is common in online websites, and some wondered why there was any controversy. Others were concerned about the absence of any consent other than the user agreement you agree to when you sign up to Facebook (and did not at the time include research explicitly). Although the effect was small, some were worried about the potential for harm given the sheer numbers involved – what if one of the users who had a more negative newsfeed had a serious mental illness? Concerns were also raised about whether ethical approval ought to have been sought as well as jurisdictional issues: where were these 700,000 users located, and was approval required in each jurisdiction? The experiment, as a collaboration between academic researchers at Cornell, and Facebook, existed in a grey area of federal regulation. It was allegedly designed