Plastic bag bans often bring with them hidden economic and environmental costs that are “virtually ignored,” according to conservative think tank the National Center for Policy Analysis (NCPA).

More than two dozen cities including Seattle and San Francisco have enacted bans or imposed fees for using such bags, but anecdotal evidence suggests that curbs on plastic bags has affected commerce in the cities where such laws have been enacted, according to a column by NCPA senior fellow H. Sterling Burnett on Waste & Recycling News’ website.

While many say single-use bags are reused, especially as trash bags, Plastics Today reports that more bans on bag use may take shape in 2012. San Francisco is reportedly looking to extend its partial ban on single-use bags. But the Science 2.0 website says that while outright bans may not be a perfect solution, they do offer a “useful way to begin reducing waste pollution.”