I think the airline practice of overbooking flights is deplorable, and hope one day someone sues over it. If there are 300 seats on a flight then they should sell 300 tickets for it. You can have a standby list on top of that, but selling 320 tickets for a 300 seat flight should not be allowed.
Yes some passengers do not turn up for flights. But the airline has already been paid for those tickets. They are not left out of pocket. And even if some passengers transfer flights at the last minute, they either have to pay huge penalties for doing so, or have paid up to three times the normal price for a flexi ticket.
I’ve never personally been affected by an over-sold flight (I guess air points status is used to decide who to not let on) but I would kick up almighty hell if I was.
If Air NZ does continue with such a policy, they should be giving a lot more than a $6 cafe voucher as compensation. I would expect to get the cost of the ticket reduced by at least 50%, a complimentary Koru Club pass for while you wait, and if you have to wait overnight, free accommodation.