Now that stores are charging 50c and upwards for their plastic bags (in South Africa) why don't they approach advertisers like Coca Cola or BMW to give away free bags with their logos on. Advertisers would pay the costs for a week or month etc and the major win would be that the consumers now collect these bags, so instead of being a one-time advert the advertisment would be seen plenty of times.
For supermarkets in the USA and the UK etc this would also be a great tool to market to large firms.
Please note all these ideas have a much more in depth business plan behind them. You can contact me for more info.