As a confirmed bottled-water nut, it was sobering to read Tom Standage's excellent NYT piece on the total absence of any benefits to drinking bottled water over tap water — it's not better for you, doesn't taste better, and is rotten for the environment:
It cannot be the taste, since most people cannot tell the difference in a blind tasting. Much bottled water is, in any case, derived from municipal water supplies, though it is sometimes filtered, or has additional minerals added to it.
Nor is there any health or nutritional benefit to drinking bottled water over tap water. In one study, published in The Archives of Family Medicine, researchers compared bottled water with tap water from Cleveland, and found that nearly a quarter of the samples of bottled water had significantly higher levels of bacteria. The scientists concluded that "use of bottled water on the assumption of purity can be misguided." Another study carried out at the University of Geneva found that bottled water was no better from a nutritional point of view than ordinary tap water.
Admittedly, both kinds of water suffer from occasional contamination problems, but tap water is more stringently monitored and tightly regulated than bottled water. New York City tap water, for example, was tested 430,600 times during 2004 alone.