That's all fine, but it doesn't give them the right to lecture me about my water use. If you choose to brush "dry", good for you. If you choose to bike to work, or air-dry laundry, or turn down your thermostat to save energy--again, good for you. It doesn't mean I should be guilted into making the same choices you do. I don't believe for a second that I let 3 gallons of water go down the drain when I brush my teeth (where does that number even come from? It seems ridiculously high, unless you have the water pouring out.)
Now, one thing I've noticed in our neighborhood is, everyone has lawn irrigation systems. Including us, but ours has been broken since we moved in. They are all on timers, so the lawns get watered every morning, even if it's pouring rain out. We even have one neighbor whose system is clearly broken, that just pours water into the street every single day. Why they don't turn off their system until it's fixed is beyond me, but there you have it. Any given lawn system uses more water in a day than I could possibly brush with in a year. But, so what? Not my lawn, not my water bill, not my job to pester the neighbors about their choices.