For me I try to limit the amount of tap water I drink for one reason: Fluoride and Chlorine.
Fluoride was introduced after scientists found that it was beneficial to reduce cavities. Unfortunatley, now a lot of people have too much fluoride in their systems which is called
dental fluorosis. Fluoride is toxic and was actually used by the Nazis and Russians as a tranquilizer for prisoners. Many scientists that were pro flouride when the program started are now anti-fluoride.
So if you live in calgary, you're showering, cooking and drinking fluoride if you use tap water for those activities.
There are some reverse osmosis filters that take fluoride and chlorine out of the water, however brita and pur filters do not.
Now the thing you have to worry about with bottled water is chemicals from the plastics used. You should avoid cloudy plastic bottles because they excrete chemicals into the water that you're drinking.
Right now i'm drinking bottled water with no fluoride content, and a minimum of other minerals. When I purchase a reverse osmosis filter for my home, I will use the water from the tap.
Also, there is fluoride in your toothpasteand mouthwash if you use any of the large brands. Thats why it says "Do not swallow" and "use only a pea size for children". I use a non-fluoridated toothpaste. I figure if it says, "don't swallow" on it, I probably shouldn't be putting it in my mouth.
Here's a link to a scientist who was pro-fluoride, until recently:
http://fluoridealert.org/limeback.htm