For me it comes down to taste. "Clean" means nothing if the water has "clean" (harmless) byproducts that make it taste like crap.
That's why I use brita filters at home. It "cleans" the water a little I suppose, but for the most part it really just makes the water taste a whole lot better. That's why on occasion I buy bottled water. Aside from the convenience of not having to carry good-tasting water around, being able to procure good-tasting water is the objective. If the tap water doesn't taste good and I don't have access to my brita filtered water, then it's probable I'll spend a little on bottled water because I don't like drinking water that doesn't taste good.
On top of that, public water fountains are a great way to pick up various viruses. My job depends to a certain extent on staying healthy, so I'm willing to spend a bit to buy water instead of drinking out of a fountain that some kid slobbered on a few minutes earlier or which was used by some moron who doesn't wash his hands after taking a crap.
I've come to the conclusion that people who bag on bottled water never leave their homes and have no taste buds. That makes them someone to pity rather than valid sources of consumer information
