I tried not washing my hair with shampoo for a period of 4 months in the hope that I could live more "naturally".
It didn't work.
My hair looked greasy and it was very difficult to brush.
So I am glad to report I started using shampoo again a few weeks ago and my hair is back to its normal shiny and grease-free status :D
Though my experiment failed I have to say that I'm glad I tried...