Once departing Auckland, Air New Zealand had a lady with a scale making spot checks, she didn't create a back-up queue, but if her scale was just being vacated and you were next - tough, Gotcha ! I was a little overweight,max. allowable 7kg. but was allowed to lighten the bag by filling my pockets and carrying my computer and book, rule satisfied I was then allowed to proceed - and then re-loaded my bag once around the corner.
QED.
I can see the need to restrict maximum weights in overhead lockers.
It is my New Year's ambition to travel with nothing but my passport in my shirt pocket - i.e. the same resolution that I have failed to keep for the last 50 years.