Sorry to burst your bubble, but a lot of the time there is no mountain, no flowing spring. The source, in Dasani's case, is a Coca-Cola plant in Jacksonville, FL. If you consider this corporate summit a mountain, then climb on.
At least 25% of all bottled water is bottled tap water - some place it as high as 40%. Of course Dasani is purified and enhanced with minerals, but it doesn't come from any mountain spring!
Generally, standards for bottled water are less stringent than those for public water systems. There is no guarantee that bottled water is high quality. The National Resource Defense Council recently tested 103 brands of water, and found that one third of the brands contained contamination.
A good article can be found at:
http://www.nrdc.org/water/drinking/nbw.asp
Personally, I think that the municipal water supply is fine. I also think that bottled water marketing goes after emotion, and tries to make people forget logic.
The simple fact is that most cheap bottled water is bottled tap water. I drink lots of water, and have NEVER had a problem drinking municipal water. (even in many third world countries from Africa to Asia)
If you genuinely sense a difference in taste, then go ahead and buy bottled water. If you are doing it for "health" reasons, you're probably wasting your money.
Of course this is just my opinion!
As the saying goes... buyer beware!