I don't think you and parent disagree. Facebook will do a good job of 'protecting' your personal data because that allows them —exclusively— to benefit from it. Though the definition of 'protecting' might differ, Facebook's might sacrifice that protection to benefit at any point. As a user, you're not in control of that transaction and will never benefit.
Also lets not forget Facebook as to appear somewhat protective of data, or they'll scare off even more user. Negative consequences of users sharing their data have to appear dystopian fiction.
