It may be a risk but I think it is the right one - taking risks is what helps you keep moving forward! I think last year's Business Week article explains well why some faith can be put in Indra Nooyi through the risks http://www.businessweek.com/magazine/content/07...
But it's not just tap water. Most of these companies purify the water before bottling it. Aquafina, for example, says on their website that they put the water through a 7-step purification process that includes reverse osmosis.
You cannot always rely on your tap water being that clean and pure after traveling through city pipes and your home's pipes. And some cities have algae, chlorine and lead problems in their municipal water. Yes, when you are at home you can put a filter on your tap. But what about when you are out running errands and already finished what was in your Nalgean bottle? I still enjoy the convenience of that and don't think that tax is really fair. If they can tax that, what's next? Anything with packaging that is not completely environmentally friendly? ...that list would include a lot of products.