If you don't regulate truthfullness of published efficacy info, then companies will compete on advertising and bad studies to claim efficacy of their products. I don't think that would lead to a marketplace where non-experts could reach correct conclusions about efficacy. I have no real idea about the efficacy of most non-regulated things I'm sold, from deodorants and toothpaste to computer software. It's just that with these things, the risk of occasionally buying something bad and learning not to use that anymore is acceptable. Not so with medicine.