Sorry for checking in late on this subject, but I just read the most recent ChowNews. In my opinion, bottled water is one of the biggest scams imaginable. In addition to the fact that it's incredibly expensive -- more per gallon than gasoline -- bottled water is almost completely unregulated. Tap water in the United States is, in general, far more heavily regulated, is tested almost continuously, and is usually equal to if not superior to bottled. Additionally, when the public drinking water is contaminated, (remember Milwaukee's problem with cryptosporidium a few years back?) it's made public almost immediately. Of course by then, it might be too late for some. Hetch Hetchy water is supposed to be some of the best you can get, but I find it has a funny taste. My solution is to use tap water, but filter it, which helps clean it even more. I believe the Pur filters even do filter out cryptosporidium. And for Jim who's concerned about the filters, if you use your pitcher regularly and replace the filters when you should, you shouldn't have to worry about microbes.
Another problem with bottled water is that it means that many more plastic bottles, and even if you are recycling, that process adds contaminants to the air, the soil, and the groundwater. That's why reduce comes before re-use and recycle.
Attached is a link to some interesting info from the Natural Resources Defense Council.