I know this is a long time after this thread was active but I have just read it so others may as well. I felt I had to reply as Madame Cholet is the only other person I have come across who has done this.
I haven't washed my hair with shampoo (except to remove something unpleasant a couple of times) for the last thirteen years. It was cut short when we crossed the equator while on a very dusty safari in Africa, I stopped shampooing it at the same time. Everyone was fairly smelly and dusty on and off for five weeks with limited washing facilities, so it went un-noticed. I had wanted to try it before, after seeing the documentary mentioned above but was worried about the nasty three week period while it settles down.
I rinse it through with plain water every day mainly to make it lie flat after sleeping, its still quite short so is practically dry with a quick towel rub. Because it isn't greasy dust doesn't stick to it. On the odd occassion I do work up a sweat and dirt does stick, it washes clean in the shower in less than a minute. No more washing, rewashing, rinsing, conditioning and rinsing again.
I've mentioned it to a few friends and they have said they wouldn't have known.
A funny aside with the short haircut was when I got home from Africa, the number of friends who ignored the wife and me in the street as they knew I was away for a long holiday and thought she was out with another bloke.