My primary take-home from having DOD/DOE security clearances, and having to sit through historical case studies every 3 months about security breaches, is that every DOD/DOE security lapses and espionage event in history were "trusted insiders" doing the deed.

Physical security was long ago solved by pre-20th century tech like locks and security guards. No, it was always a trusted insider. There's no reason to assume that is any different with social media companies.