The bottled water industry is truly silly.
It's an enormous money-maker, a $20B industry in the US alone. You're buying a product that's hundreds of times more expensive than tap water. Yet, often the bottled water simply comes from a municipal source anyway. Furthermore, it's easily less safe than your tap water. See, the EPA has tougher regulations for tap water than the FDA has for bottled water. For example, the FDA allows some contamination of E Coli, and does not require testing for known parasites such as Cryptosporidium or Giardia Lamblia. Likely your bottled water does not contain Fluoride as well.
Not to mention the insane consumption of oil required to schlepp around all this bottled water and then again to discard the empty plastic bottles. You should of course recycle them, but precious few of us actually do and so they fill up landfill, a "gift" from us to our future generations. Or perhaps your empty bottles end up in the Great Pacific Garbage Patch.
And as if all of this weren't already reason enough to avoid bottled water, there is the curious problem of the chemicals in plastic, such as Bisphenol A (BPA), leaching into the water over time. Previously, it was believed that these chemicals didn't easily leach unless the plastic was hot (this is why you're not suposed to put plastic containers in the microwave or dishwasher).
However, this delightful study showed that simply drinking bottled water increased BPA in urine by 2/3rds. Perhaps bottled water should include a clear "bottled on" date so you can at least roughly gauge how much BPA you're about to drink.
Plastic is clearly an incredibly useful material, and I'm sure we'll eventually sort out the problems of the various chemicals that leach from it. In the meantime, I simply play it safe by avoiding plastic touching our food/drink, when practical. For example, we only put glass ware in the microwave, and when we need to carry water on-the-go, we always use a Klean Kanteen. In fact we now have many Klean Kanteens: in the car, in the stroller, next to the kid's beds and in our home offices, on the dining room table, etc.