I read this article a long time ago about an attempt in Chicago to tax bottled water, and I think it's brilliant. Bottled water is one of my latest pet peeves. By all means, filter your water - it certainly tastes better than a lot of our tap water. But then put that water in a reusable bottle, like this SIGG bottle that I really want.
Disposable plastic water bottles just seem like such a waste to me, especially since I see so many of them end up in the trash can. But trying to get people to stop drinking bottled water is a hard battle to win. A tax measure can discourage people from buying so many water bottles, while at the same time generating revenue for a city. Maybe a little financial incentive will convince people to stop their wasteful ways more than arguing with them will.