I haven't sampled the procedure 'in the flesh' but my description was how I read my local pub was going to operate from it's facebook post - enter on a common sheet, then kept securely for however many days, then destroyed. Individual slips, placed immediately into a 'box of the day' I would find entirely reasonable. It's not the publican that concerns me, it's some of the other punters. I would think privacy / security of the data would be particularly important for any female customers.