I was on it a year or so ago when it was just surfacing, just to try it out and have a valid opinion, and I can fairly say it is incredibly depressing. You deprive yourself of a variety of nutritious foods, eat no more than 500 calories a day, and you're NOT allowed to exercise. Does that sound like a healthy way to lose weight? No!
It's one of these diet fads that will fade out. Once again people will learn the hard way that there are no cheats or shortcuts to weight loss, no miracle drug. There is only one equation that works, and it requires a lot of hard work and dedication!