Facebook communicated really badly about a controversial study in which it secretly manipulated users feelings, the social networks chief operating officer Sheryl Sandberg admitted Wednesday. The company clandestinely altered the emotional content of feeds of nearly 700,000 users for a week in 2012, giving some sadder news and others happier news in a study aimed at better understanding emotional contagion. The research, published last month, has prompted online anger and questions about the ethics of the research and forced Facebook on the defensive. We communicated really badly on this subject, she said, before adding: We take privacy at Facebook really seriously.