Speaking as a psychologist who's extremely familiar with both experimentation to affect emotional states and AB testing, I really, really don't see one.
I personally think there should be ethics reviews for AB tests, but that's a fringe position in the industry right now.
Consider "A 61-Million-Person Experiment in Social Influence and Political Mobilisation", the 700,000 people whose emotional states Fb experimented with, the documents which revealed how Fb tried to pinpoint when young Australians and New-Zealanders were vulnerable to advertising.
The difference between AB testing and Facebook's experiments should be obvious to anyone familiar with those experiments, as the aim has been to research and alter human behaviour in general, whereas AB testing has to do specifically with understanding user engagement and satisfaction with regards to the product.
Trying to dress up this experimentation as AB testing or no different than AB testing is incredibly dangerous. As a psychologist extremely familiar with both this kind of experiments and AB testing, you really, really should see a difference.
This article, right: https://www.nature.com/articles/nature11421 ?
So, this is a messaging experiment, which is pretty standard within psychology. The only interesting thing about this (and the only reason it's in Nature) is the size, not the experimental design.
> The difference between AB testing and Facebook's experiments should be obvious to anyone familiar with those experiments, as the aim has been to research and alter human behaviour in general
This is what AB tests do. You change the colour of the button, and conversion rate (i.e. the proportion of people that give you money) goes up or down. How is this different from people taking an action (self-reported, btw so potentially garbage) around an election? Seriously, i would love to know the actual difference here.
You may not like Facebook, hell, I may not like Facebook but it's just inaccurate to say that they are uniquely bad because they run experiments on people, when my entire career both in academia and industry has been running experiments on people and that's somehow OK.
I listed three examples that should make it obvious. You refuse for some reason to accept the obvious, that these kind of tests try to alter real world behaviour and not behaviour with regards to the product.
There's a big difference between changing a button's color in a page to see how user engagement changes and trying to find when teenagers are in a more vulnerable emotional state to serve them ads. If you can't see the obvious I'm afraid there is anything more to say.