Yes, I think there will be quite a large number of people who take the basket away and then, rather than walk all the way back to return it, will either dump it in the car park (which stores can cope with) or will stick it in the boot and dispose of it at home (or give it to friends in the scrap metal trade).
I hope we don't end up having to put a £1 in for a basket as we do for a trolley.
Here's an opportunity for youth group etc to make some money- as well as or instead of helping with bag packing they could carry your basket to your car for a small donation and then return it to the store.
I'm perhaps not very good at customer service but I think that after a month or so, once everyone is familiar with the bag charges, if it was my store I'd probably not allow anyoneto take baskets out. If they need bags they should bring their own, buy one or buy less