Before most experiments begin, participants are explicitly told that they are volunteering to participate in a study, and they are told what procedures will be used.
Then participants can decide whether or not they want to continue with the study, and know they can quit any time without penalty if they feel uncomfortable.
This lack of a rigorous ethics board has caused much outcry from academic researchers who do similar studies.
However, it is also worth mentioning that there are no universal standards for ethics boards internationally, or even in America.
A good rule of thumb is whether the potential harm of participating is no greater than what people would ordinarily experience in their daily lives (this is called minimal risk).
So in OKCupid’s experiment, the worst that could possibly happen is that a participant goes on an unsuccessful date with someone whom they met on the site.
In other words, scientists must come clean and admit the true purpose of the study when it’s done. In a typical study, the researchers will debrief each and every participant in the study (sounds intimate; it’s actually quite mundane).
It’s unclear whether OKCupid or Facebook debriefed the participants in their studies, although they did an “indirect debriefing” by making their procedures and results publicly known (and perhaps assuming that their users follow the news).
And ultimately, the net effect on people’s mood was So people’s outrage may have been a bit of an overreaction.