Want to make yourself crazy? Next time you’re driving, pay attention to the astonishing number of plastic bags on the side of the road. In the trees, hanging on fences, floating lazily through the air on a summer breeze, clogging storm drain grates.

Some jurisdictions are trying to do something about the problem. Mexico City has become the latest city to ban plastic shopping bags. Just weeks ago, a law passed in March by the local assembly became effective – with a one-year grace period during which no fines will be levied for violation of the ban.

Mexico City joins San Francisco, Mumbai, New Delhi and hundreds of other cities, as well as several countries, in banning the ubiquitous bags. Many cities and countries without an outright ban have taxed plastic bags to the point where people have virtually stopped using them. Ireland, for example, began charging for plastic bags in 2002, and, since then, usage has plummeted. The country has, in effect, forced its citizens to be more environmentally conscious.

Italy and France intend to institute their own bans next year. China and Australia have already done so.

Conspicuously absent from the discussion is the biggest user of all – the United States. While a few cities have banned the bags, they remain the exception rather than the rule, and the country continues to use as many as 100 billion plastic bags every year – some (think of the plastic bag your Subway sandwich comes in) for a mere few seconds.

San Francisco banned the bags in 2007, and the Los Angeles City Council unanimously passed a ban to become effective in July 2010. However, since then, questions have arisen as to whether an Environmental Impact Report (EIR) would be necessary under the California Environmental Quality Act. According to Paul Backstrom, the Field Deputy for LA Councilman Jack Weiss, that looks likely. Such a report would focus on “economic impacts to industry and small mom-and-pop shops.” And, Backstrom says, no one is sure how the city would fund the EIR.

Plastic bags do have their champions. The Save the Plastic Bag Coalition has fought plastic bag ban proposals in Oakland, Manhattan Beach, LA County, Palo Alto, Santa Clara County, San Diego, Santa Monica, Mountain View, Morgan Hill and San Jose. Its website argues that “Paper bags are far worse for the environment than plastic bags. Paper bags result in 3.3 times more greenhouse gas emissions than plastic bags. Paper bags use up 2.5 times more landfill space than plastic bags. Not to mention the trees.”

It is true that the manufacture of both paper and plastic bags involves significant resources. It also is true that paper bags take up more landfill space than do plastic bags. Then again, unlike paper, plastic takes hundreds of years to degrade. And the very thing that allows plastic bags to take up less landfill space – their light weight – also allows them to ride a stiff breeze to the tops of trees. (Then again, tens of millions of trees are needed to produce the billions of paper bags manufactured annually, so trees with bags in them or no trees?)

Many environmentalists argue that banning plastic bags and not paper bags isn’t really helping matters. They would argue for banning both and encouraging the use of reusable bags.

Currently, California courts aren’t universally friendly toward plastic bag bans, mostly holding that local jurisdictions must prepare EIRs, an exercise that often is beyond their financial capabilities. And, just as public opinion looked like it was moving inexorably toward support for such bans, the economy soured, and even fairly affluent and liberal Seattle voted down a usage fee.

And, as New York Times reporter William Yardley pointed out in an article about plastic bag bans nationwide , environmental groups aren’t making such bans a top item on their agendas, which, as he noted, are more likely to “focus on broad federal issues like carbon emissions, renewable energy and use of public lands.”

In the end, the answer to the question at the end of the checkout line – “plastic or paper?” – is currently best governed by personal preference and values.