Seems we could do something more productive with these data than encourage a sad teen to buy something as a "confidence boost". But, according to this article by MIT Technology Review and Ars Technica, it seems the data was used in this way. Facebook has responded to this article here, and corrective steps are being taken.
For reference and further reading:
- MIT Technology Review article: "Is Facebook Targeting Ads at Sad Teens?"
- Ars Technica article: "Report: Facebook helped advertisers target teens who feel “worthless” [Updated]"
- Facebook response