These Face recognition cameras are using in two purpose. One is for keep as a data base of peoples
Gathering anywhere or any identified places, Identify specific objects, behavior or attitudes in video footage. As on the roads, shops, functions, etc.
Second way is,
It is used for intrusion detection. It uses biometrics to map facial features from a photograph or video. It compares the information with a database of known faces to find a match. Such as someone caught on CCTV suspected of committing a crime, against a database of custody images as it assists them in identifying people who have committed crimes.