In 10,000 years, when archaeologists excavate the remnants of late 20th- and 21st-century civilization, they will find a dominant artifact: the plastic bottle.
Americans throw away 60 million plastic bottles each day, most of which wind up in landfills. In response, several cities, including Minneapolis and San Francisco, are encouraging residents to wean themselves from bottled water and switch to tap. In addition to the massive waste problem, consider the environmental impacts of manufacturing plastic—fossil fuels, air emissions—and of shipping the water from France (Evian), Maine (Poland Spring), California and points beyond (Crystal Geyser).
If you're worried about water quality—such as those Durham households whose water tested high for lead—then bottled might be an option. Otherwise, a filter on the faucet will likely do the trick.