Is there a difference between A/B testing which surveys "taste" and A/B testing which causes "behavior change"? There is the small matter of side-effects..
I am guessing somewhere below their duty to their shareholders?
That was sort of snark at Facebook, but it is a difficult legal question. However, it also sounds like a bit of a beat-up, like the Strava lawsuit.
You are not gauranteed by Facebook for a service that allows you to communicate in a clearly defined way. They are allowed to, an do, tweak it constantly to improve whatever metric they think will result in more engagement and bottom line. Much like google tweaks their search results (or their cafeteria food) these companies are always running experiments. In this case, it resulted in a paper. The researchers who published the paper might have to ensure they upheld the ethical obligations of the journal, and any affiliated institutions. If they did, the fact this is published is a better outcome then normal.
