Already four years ago they ran experiments [1] on how to program your mood. They built an API to your emotions, and they started selling it, without you knowing it.
[1] https://www.nytimes.com/2014/06/30/technology/facebook-tinke...
[1] https://www.nytimes.com/2014/06/30/technology/facebook-tinke...
To my mind, there is something inherently wrong about the techniques used to sway opinion about products and services. They prey on our animalian reflexes and bypass the part of the brain even capable of consent. Marketing "should" (and I don't use that word often) be prohibited to use such tactics, and instead be an exposition of the product and service and any traceable, trustworthy qualifications bestowed upon it. Such a system is still hackable (selling awards for instance), but it's a way better alternative to marketing practices than what we have today.