If people are really green conscious, they shouldn't be
consuming so much or driving. Plastic bags only make up a small
percentage of total rubbish generated per household. Sometimes, I
think "green efforts" are barking up the wrong tree.
From the business angle, I don't think seeking discounts for using
less plastic bags will change consumer behaviour. However,
businesses may take to the idea of using a "green" excuse to charge
$0.10 per bag and thus make more money.