"Within weeks, 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."
Motivated by a Tax, Irish Spurn Plastic Bags (The New York Times).
Legislation, at least when it includes a hefty tax, is clearly an effective means of bringing about social change-more effective than advertising campaigns or the efforts of individual retailers (like Whole Food's 5-cent discount per re-used bag in the United States). Write to your government officials and let them know you'd like to see plastic shopping bags disappear the way they disappeared in Ireland.