nightclubs want lots of customers especially attractive women, and don't want lots of problems. What's the potential for abuse? Detecting your attractiveness or ethnicity in order to turn you away would be abuses, but is that what you are thinking of or alleging? because if it's just facial recognition, they don't have an incentive to misidentify people

This is indiscriminate data collection. Some of the risk comes from the correlation with other sources of data by LEO with overly broad access to fine grained data.

Big Brother is not watching you. Instead, thousands of Little Brothers are patiently watching their little corner of the world, recording license plates, logging phone locations, tracking credit card usage. Big Brother doesn’t need to see you, he just asks them to tell him what he wants to know.

if anything is stored, "we know you were at this night club at this time" is pretty sensitive information? depending on the kind of club.