I work on Big Data for a living and know how inept companies are at actually doing anything useful with personal data. The data being generated is massive and the vast amount of it is random and useless.
My reason for reducing my social media presence is the Like count next to every thought expressed. By adding a publicly visible number next to every expressed human thought, you influence behavior and thinking. This has all kinds of consequences that tech corps and society are waking up to - ledger.humanetech.com
That is why I have consciously reduced my social media usage.