SAN FRANCISCO -- Facebook's team of data scientists who had access to the daily lives of nearly 1.3 billion users at their fingertips operated with few limits until recently, the Wall Street Journal reported Wednesday.
Had the researchers worked for a university, they would have been required to get consent from participants in a study.
But Facebook decided that users provided their consent when they agreed to the company's terms of service.
The terms of service at the time said data could be used to improve Facebook's products. The terms now say that user data can be used for company research.
Facebook says it has tightened guidelines for data research.
The work of these two dozen or so data scientists came to light after research was published about a 2012 experiment in which the news feeds of nearly 700,000 Facebook users were manipulated to see if their emotions could be swayed by positive or negative updates from friends and family.
Facebook users did not give the experiment a thumbs up. The revelation triggered a torrent of outrage with many taking to Facebook and other social media to protest being the company's guinea pigs.
Facebook Chief Operating Officer Sheryl Sandberg said Wednesday that the week-long experiment was part of ongoing research to test products and was poorly communicated.
There's no review process, per se, Andrew Ledvina, a Facebook data scientist from February 2012 to July 2013, told the newspaper.
Anyone on that team could run a test, he said. They're always trying to alter peoples' behavior.
Jonathan Hirshon, principal of Horizon Communications, said behavioral research is laudable but only when people know about the research and consent to it.
With big data comes even bigger responsibilities, Hirshon said.