To start with, around these parts, at least, bottled water is (a) often less pure than tap water, (b) by far more poorly regulated than tap water, and therefore (c) not as safe as tap water, and, besides, (d) often doesn't taste as good. Tap water is regulated by 100s of people at the EPA, while there is one official at the FDA whose duties include oversight of bottled water. For more on this, and also some amusing blind taste tests demonstrating point (d), see Penn and Teller and 20/20.
But that's not all. The above points just show that bottled water is kinda dumb. But, more than that, the bottled water industry is also evil: in short, it works to falsely undermine public confidence in tap water, to actually undermine the quality of public water resources, and to privatize water resources. In the long term, Satan's spit corporations have their eye on a future in which they control the water supply as population growth and global warming lead to increased demand and decreased supply, which, for them, would equal profit.
No Impact Man has provided a summary of the evil corporate conspiracy underlying the rise of bottled water, comparing the future of water to what we have seen with oil. And we see this underway here (No Impact Man quoting BusinessWeek).
In the coming decades, as growing numbers of people live in urban areas and climate change makes some regions much more prone to drought, water—or what many are calling "blue gold"—will become an increasingly scarce resource. By 2030 nearly half of the world's population will inhabit areas with severe water stress, according to the Organization for Economic Cooperation & Development. [Evil water privitizer T. Boone] Pickens understands that. And while Texas is unusually lax in its laws about pumping groundwater, the rush to control water resources is gathering speed around the planet. In Australia, now in the sixth year of a drought, brokers in urban areas are buying up water rights from farmers. Rural residents around the U.S. are trying to sell their land (and water) to multi- national water bottlers like Nestlé (BW—Apr. 14). Companies that use large quantities of the precious resource to run their businesses are seeking to lock up water supplies. One is Royal Dutch Shell, which is buying groundwater rights in Colorado as it prepares to drill for oil in the shale deposits there.And here is a handy selection of further quotes. Also word of an upcoming documentary.
There is also the absurd waste of resources involved in the packaging and transportation of bottled water, but I won't get into that here.
Anyway: Please don't drink bottled water. And bottled-water-free zones are popping up in city halls and campuses and whatnot (there is no such thing here that I'm aware of, but I am eying the well-documented record of the successful campaign at the University of Winnipeg), so support those if they come your way--individual boycotts alone aren't going to defeat Satan's spit.