Wasting water
Agree or disagree, I love contrarian views like this: "Purifying millions of gallons of water to drinking quality only to have most of it used for purposes that do not require drinking-quality water seems potentially more of a waste than a couple of billion pounds spent on what little water is used for drinking." As someone points out in the comments, "a study [would need to be done] of how much contaminants in non-potably-purified water can still cause illness via washing, teeth-cleaning etc would need to be factored in."
Also from the comments: "Bottled water competes with soft drinks, not the mains. What are the comparable environmental and cultural affects of coca-cola, as comapared with water? Coca leaves and kola nuts come from Latin America and Africa - lots of air miles clocked up there, I should think, and I cannot imagine the Coca Cola company pays highly for them."