Maybe I'm just a purist in this case. I think that juice fasting is a means to an end. A slower way of cleansing or losing weight than water fasting, but I wouldn't think it would be good for the body to continue indefinitely any more than it would be to continue Water Fasting indefinitely. The body admittedly needs rest from digesting foods at times but complete rest for ever? It's a natural bodily process and as good as juicing is it isn't utilising the whole body, and once the goal of the juice fast is achieved, just like water fasting, the body needs to get back to 'normal'.
So while I wouldn't call it a starvation diet as such, I would hesitate to suggest that juicing is providing everything that the body needs. Don't ask me about the Lemonade Diet , it doesn't sound like something I would like. :p