I don't think this scenario could play out that way.

- Facebook profiles can be made inaccessible to non-friends. People who post pictures of themselves naked and using drugs use this feature.

- The hypothetical conclusions drawn are only possible if users post extremely frequently and in great detail. Otherwise, the predictive analytics will suffer from garbage-in-garbage out. Huge companies spend millions of dollars collecting decent data, and the claim here is that a 16 yr-old's facebook profile will have high quality data.

- If the situation presented in the article gets even close to coming true, people will know about it and compensate. The end game won't be all-knowing companies, it'll be SEO for social media profiles that make people look good for a fee.

[edit: removed meanness]