Having read the ingredients on the back of various hair-care/bath products I came to the conclusion, that they are all pretty much of a muchness.
Biggest ingredient; Water (Aqua!), then Sodium Laureth Sulphate etc etc. If I ever run out of shampoo, I'll often use condtioner or even Radox to wash it with - and to this day have suffered no ill effects. My hair is still clean, fragrant (!) and not a massive ball of frizz.
I think the advertisers talk a lot of rubbish when it comes to hair products. It used to say on shampoo bottles, "Wash and Repeat", now it usually just says "Wash and Repeat if desired"...i.e if you want to use twice as much of their product each time you wash your hair, then please do so!
Further information can be found in my thesis, "Vosene, it's part in propagating the rise of hair fascism" �9.99 from all good bookshops.