"The soft drink giant Pepsi has been forced to make an embarrassing admission: Its bestselling Aquafina bottled water is nothing more than tap water. Last week, Pepsi agreed to change the labels of Aquafina to indicate the water comes from a public water source. Pepsi agreed to change its label under pressure from the advocacy group Corporate Accountability International, which has been leading an increasingly successful campaign against bottled water."
I stopped drinking bottled water a while ago for these reasons:
1. The monetary cost. This article that I quote above, suggests that bottled water is 7,000 times more expensive than tap water. And, this points out, it's tap water they are selling. I didn't want to be a sucker.
2. The cost to the planet. All that plastic. Most of it non-recycled.
3. Regulations. Our Buffalo tap water is closely monitored by the authorities (PDF). bottled water isn't monitored by the FDA, a body that has zero authority. Although they have a handy article about it.
My advice. Bottled water is when you can't get to a tap. Tap water is when you can.