Facial recognition is only the beginning. As seen in "Psycho-Pass" (a Japanese cyberpunk anime), a powerful network of psychometric scanners are deployed to actively measures the minds and mentalities of people using "cymatic scan" of the brain.
It's possible to conceal your emotions with "poker face" to a primitive facial recognition system. But it'd be difficult to hide from functional magnetic resonance imaging (fMRI) scanners. For now the technology is not viable for mass remote scanning, but sooner or later they'll figure out something that works for mass brain scans.
Imagine in the future, you get angry and your emotional state is picked up by a scanner. You receive a multimedia message from HealthyOutcomesCareNetwork(TM) containing soothing audio and images. If your emotional state remains volatile you'll receive a call from AI shrink and medication delivered to your door by a drone. If you refuse the medication and your emotional state doesn't improve, a white van will come to pick you up and send you to a rehabilitation facility, with time-off notices automatically delivered to your place of employment (if you still had a job).
Those who are incurable and deemed danger to society will either be placed in permanent detention, or drugged up and sent to an incinerator.
