Facebook is facing backlash from users and researchers over the ethics and legality of a recently revealed week-long experiment, which the company conducted in January 2012.

The company secretly manipulated the news feeds of nearly 700,000 users and found that the information posted by a user’s friends can influence that user’s mood.

The experiment took place Jan. 11-18, 2012, the week before the massive online protest against the Stop Online Piracy Act and the Protect IP Act. The findings were first published June 17 in the Proceedings of the National Academy of Sciences of the United States of America—the official journal of the U.S. National Academy of Sciences.

Adam Kremer, Facebook data scientist and the study’s lead author, posted a public apology on his Facebook page, stating that his research team did not clearly state the motivations of the study, which, he says, were to understand if friends’ negative emotions led people to avoid using Facebook.

“In hindsight, the research benefits of the paper may not have justified all of this anxiety,”said Kremer.

So far, the Federal Trade Commission has been silent on the matter, but Facebook already landed in hot water once when the agency charged the company in 2011 over deceptive user privacy practices. The commission acts as the federal government’s consumer watchdog, promoting consumer protection and working to prevent monopolies.

Read more on Watchdog.org.