[kevingadd]

You seem to assume that A/B testing is implicitly ethical and this is unethical. That's not the case. The reason this experiment is considered unethical is due to the specific details of the experiment and other common A/B tests could easily be considered unethical if examined using the same criteria.

This particular experiment is getting scrutiny because they published the results in a journal and it is a rather egregious example (the hypothesis, and test methodology, both demonstrate a particular brand of recklessness you don't tend to see in website A/B testing.)

EDIT: For reference, I know a lot about this subject because I worked extensively at IMVU, one of the first consumer-facing websites to aggressively A/B test almost everything. I don't have a luddite perspective on this.