They've been doing this for I don't even know how long in Japan. I think it's funny that they're calling this some sort of "new" treatment here. It's actually very commonplace in Japan, and I have a friend who went and did it. No big deal.
Why have fish eat your feet when we have things like pumice stones and callus files? Seems kinda gross to soak my feet in fish and have them make waste in the same water.