I guess this really shouldn’t be a surprise that this happened. We already knew that FaceBook were conducting experiments on users judging emotional responses to positive/negative articles in newsfeeds. At the time I don’t think many really extrapolated this as a possible end result however.
What FaceBook has done isn’t (I don’t believe) inherently wrong, it has simply put a power information warfare tool in the hands of those who want to buy it with few controls to govern its usage . Whether this was intentional or not will never be known of course, but the fact remains the capability has been created and is now in the wild.
This article isn’t particularly in depth on the issues this brings up but it does describe a very simple example of why this capability matters and why something should really be done about controlling its usage.
https://www.newyorker.com/news/news-desk/cambridge-analytica-and-the-perils-of-psychographics