The flip-flop-flip by supermarket chain Coles this week over whether to give away plastic bags is not the most important problem facing the country but it has provoked an unusually sharp debate about how to take collective decisions to solve community problems.

To recap, the two main supermarkets - Coles and Woolworths - voluntarily decided a few months ago to ban single-use plastic bags because environmentalists complained the bags clog up waterways and kill wildlife. This particularly affected NSW, the only state to have not announced a ban.

Coles will give its "Better Bags" away for free until August 29. Credit:AAP

The supermarkets decided to cater for shoppers who forgot to bring their own bags by selling thicker reusable plastic bags for 15c. The price was just high enough to offer to their customers a gentle incentive to get their act together and bring their own bags next time.

This Wednesday however, after a sustained campaign by shock jocks and complaints from customers, Coles did a volte face and announced that it was breaking ranks. It would start giving the thick reusable bags away for free. Bag-toting environmentalists immediately complained on social media, pointing out that the free thick bags would be dumped just like the free thin ones but causing even more environmental damage. By Thursday Coles thought about it again and executed a second backflip. It promised to return to its first decision and start charging for the recyclable bags again from the end of the month.