There is a potentially disastrous blow to FB's business model in the GDPR that relates to this sort of profiling. It is forbidden under GDPR, unless the user grants explicit consent (opt-in). See [1].

Without this, FB's targeting abilities for ads just evaporates. It is going to be interesting to see how this pans out.

[1] https://ico.org.uk/for-organisations/guide-to-the-general-da...