I've been tempted many times, fantasising about how facial recognition could be used to positively impact society. Imagine having the consequences of being a jerk to wait staff being that you can't go to any cafe for a few weeks. Imagine if being abusive to the kids in Colesworth/Aldi etc leading to a ban from those stores for a bit. Similar story with Bunnings - abuse leads to being banned from all Bunnings stores.

It has potential to really improve customer behaviour. If going on an abusive tirade at some kid lead to you being banned from going into stores, it would make you really reconsider whether you wanted to act that way. Then I wake up and think about the numerous ways the technology would be abused: Bad breakup with an ex, and they've put you down as being abusive from all the stores in revenge. Quietly profiling people based on their spend habits (This person is not profitable, give them a lower priority). It's a nightmare - something that doesn't sound too bad, until you really think about how it might be used.

It's beside the point though, as this behaviour is clearly against the Privacy act. Here's a quick reference of Australia's Privacy principals. On the surface, they appear to be in violation of:

APP 1: Personal information has been gathered in a way that is not open and transparent.
APP 2: As Bunnings haven't disclosed this activity, they have not given people the option of opting out.
APP 3: There are only certain scenarios where a business can collect personal information. Long story short, it needs to be a requirement of providing a service. They don't need a facial scan of all their customers to sell hardware, so they aren't entitled to collect them in the first place. They may be able to debate this point on the issue of staff safety though - but it's not a sure thing.
APP 5, 12 & 13: Obviously they're in violation of APP 5, 12 and 13 - since they didn't disclose collection in the first place.