In Ireland, you have to pay a 33-cent tax for every plastic bag you use. "Within weeks [of the law's passage], plastic bag use dropped 94 percent. Within a year, nearly everyone had bought reusable cloth bags, keeping them in offices and in the backs of cars. Plastic bags were not outlawed, but carrying them became socially unacceptable — on a par with wearing a fur coat or not cleaning up after one’s dog." via New York Times