Good comments. A lot of this revolves around things people debate about all diets. Is a fast good for you? Do you have the will power to do it? Will you lose fat or muscle?
I also noted that this diet would be hard to pull off at work (which is why I suggested it be tried on a "stay-cation" when someone was at home).
People who say this can't work simply don't understand conservation of mass, however. It's a remedial physics concept...mass can't be created from nothing. It would have to work if you could stick to it.
I've never tried it and doubt I ever will, because I don't think I have the will power for it because I can imagine having to go an entire day or even longer without eating, but I bet there are people who would be able to stick to something like this and who would lose weight.