@ Frizzle – It may be a fad, but I have to say it has worked for me. I have to avoid sulfates because my scalp reacts badly to them nowadays. Because I avoid sulfates I need to avoid silicones, unless they are of the water soluble variety. My hair is wavy/curly and I shampoo twice a week in winter and, generally, every other day in summer. On days when I don’t use shampoo I use a no silicone conditioner to wash my hair. Right now that no silicone conditioner is Suave Naturals Tropical Coconut.
When I first heard about/read about the Curly Girl (CG) Method I thought it sounded crazy. But I decided it might be crazy enough to work. And it did, and does, work for me. Just so you know, before I stopped shampooing every day my scalp was oily and the ends of my hair were as dry as a desert. Now the scalp is much more normal and the ends are no longer dry.
As to the science, if any, behind it? The Brains will have to answer that one. All I can offer is personal experience.
Hope that helps.