Last night I had a dream. (No, this isn't a parable; I literally dreamed this last night.)
People wore a VR device that could also monitor the person's health. Facebook used that to monitor the user's use of oxygen, and used that to drive engagement - the more oxygen they were using, the more engaged they were. (I say "Facebook", though in my dream I didn't see a logo. It looked like an FB-style feed, though.)
That is, they were driving engagement to the point where it became a physically measurable load on the user. "Engagement" became a sap on their physical energy.
Just a nightmare?