...Ditto on something like solar power--it sounds good in theory, has potential in practice in parts of the world, but it's not going to catch on in New England as a major source of power...
Actually, I love my New England solar panels! Precisely
because I'm so far north, the same side of my roof is facing the sun almost the whole day. While we couldn't go off-grid with them, they do help a lot in reducing our electric bill. (I think our current record is under ten bucks!)
As for the original topic, I haven't seen the ad in question, but I was always taught to shut off the water while brushing my teeth. Even if there's plenty, it's going from the "clean" side of the system to the "dirty" side, so it does seem like a waste.
But I believe in balance, and I don't think we have to make a choice between perfection or not trying at all. I certainly don't do everything some people do. (I flush my regular toilets, and I love my hot showers.) But I do turn off the water when I brush. And I recycle...most of the time. It's one of those things were a lot of little contributions add up, and every little bit helps.
And while we can't realistically ship our excess water right where it's needed, if the ad makes us stop and think, maybe we'll come up with something else we can do do to help.