A trichologist (sp?) on the radio today said that if you suffer from thinning hair then try washing it with water ONLY for a few weeks. Many people notice a big improvement by not using soaps or detergents, ie, shampoo. Apparently a lot of the 'miracle' hairloss products are actually just water-based formulas that smell nice and contain no actual soap/detergent.
I've always had a small, thin patch at the front of my head which I can disguise with the right hairstyle, but I'm going to try this and see what happens.