The city of San Francisco is planning on banning the use of Styrofoam, or more technically, polystyrene containers. The ban would take effect on June 1st, and would require city restaurants and government agencies to stop using polystyrene containers. See the details of the proposed law here. The new law was created because the manufacturing of the material involves polluting chemicals, and it is blamed for cluttering landfills.
San Francisco also recently banned the use of plastic bags.
See also: IKEA To Start Charging For Plastic Bags