My mum bought into a lot of homeopathy and Bach flower remedies. Thought she was doing me and dad a favour by getting both, and even "secretly" gave dad doses of the latter (and I was a kid so didn't have much say), so I was fortunate both categories were basically nothing.
But her and dad?
One of the Bach flower remedies was "for memory"… she got Alzheimer's about 20 years younger than her mother.
When my dad was dying of cancer, there was some mineral he thought he was short of (magnesium?), and he didn't realise the homeopathic pills labelled "magnesium" didn't actually contain any magnesium.
Sure, but look at homeopathy. It's like a virus - you don't optimize for killing the user, because a dead user can't buy more meds, and also you might get sued. Instead you optimize for having as purely placebo an effect as you can. (It's also cheaper.) For that reason, I suspect the scam market is already saturated. Will some people get scammed into taking dangerous chemicals? Sure, but that's already the case cause those aren't regulated as medications.
IMO, prevent use of addictive ingredients, but beyond that inform, don't forbid.
I see where you're going with that, but history has demonstrated widespread use of substances where the risks were long-term and/or mild and so the selection pressure you describe wasn't sufficiently fast-acting, some of which are now regulated or banned, and others are still widely available — off the top of my head: Radium paint; Victorian-era cosmetics containing lead, mercury, arsenic, etc.; alcohol and nicotine in general; atomic explosion testing as tourist attractions; indoor wood fires to make places seem more cozy; electrolytic foot spas; ionic bracelets; asbestos.
Several of these involve housing. IMO it makes sense to regulate safety in the housing market because the housing market is broken - I would not be surprised if at least in some cities, complete knowledge of the consequences of asbestos in the walls wasn't a deterrent even if the renter was fully rational. With those that don't, I think full information and personal responsibility is still the best approach. Do you want the cancer creme or the non-cancer creme?
That said, I think we would get most of the benefit of regulation if we just required an advisory consultation with your GP before you could buy a product whose safety wasn't established. A lot of the danger of overregulation rests on trivial inconvenience vs outlawing experimentation, and I think something like that could split both groups. "Yes, I want to enable experimental mode on my body."
