Updated, Sunday, 6/29, 9:54 p.m. Eastern.

Catching a glimpse of the puppet masters who play with the data trails we leave online is always disorienting. And yet there's something new-level creepy about a recent study that shows Facebook manipulated what users saw when they logged into the site as a way to study how it would affect their moods.

But why? Psychologists do all kinds of mood research and behavior studies. What made this study, which quickly stirred outrage, feel so wrong?

Even Susan Fiske, the professor of psychology at Princeton University who edited the study for Proceedings of the National Academy of Sciences of America, had doubts when the research first crossed her desk.

"I was concerned," she told me in a phone interview, "until I queried the authors and they said their local institutional review board had approved it—and apparently on the grounds that Facebook apparently manipulates people's News Feeds all the time... I understand why people have concerns. I think their beef is with Facebook, really, not the research."

Institutional review boards, or IRBs, are the entities that review researchers' conduct in experiments that involve humans.

[Update, Sunday, 9:54 p.m.: But there seems to be a question of whether Facebook actually went through an IRB. In a Facebook post on Sunday, study author Adam Kramer referenced "internal review practices." A Forbes report, citing an unnamed source, said that Facebook only used an internal review. When I asked Fiske to clarify, she told me the researchers' "revision letter said they had Cornell IRB approval as a 'pre-existing dataset' presumably from FB, who seems to have reviewed it as well in some unspecified way... Under IRB regulations, pre-existing dataset would have been approved previously and someone is just analyzing data already collected, often by someone else."