I don't agree with a juicing diet either.
Actually, I am pregnant right now, and my doctor advised me to eat whole fruits rather than the juices-because it is more nutritious and you are getting the fiber, etc. that the juice omits.
It is okay to make a smoothie with your fruit (as in throwing a whole banana and some berries in the blender with ice, etc.) because you are still getting the whole fruit-it is just in a pureed form and still retains the fiber content-but juice alone where the fruit pulp is tossed away-is not as healthful.
I also think that a proper diet needs to be balanced. Fruit and veggies are a wonderful source of vitamins, but you also need to be sure that you are getting in enough protein in your diet to fuel your muscles and regulate your blood sugar-as a diet of fruit juice alone is all carbohydrates, and you will lose muscle mass by omitting protein.