The DC tax on disposable bags once routinely distributed at supermarkets has cut use by "more than half" since it took effect at the start of the year. Bag use is dropping at a higher rate than expected. I wonder how fast they expected demand to drop: did they perceive a huge demand for single use bags?
My favorite critique of the bag tax is that it will disproportionately hurt the poor. It seems to me that the poor are likely to learn very quickly that they need to bring reusable bags or at least the bags they paid for last time. A little tax works wonders!