Re: What's the harm?
Of course the alternatives to snake oil, up until the 1960s even, were calomel and arsenic. The pharmacists of the 19th and 20th century dispensed many mercurials, not just calomel. Calomel pills were used in acute and chronic diseases and as a diuretic drug before the organomercurials appeared in the 1920s. Skin diseases were treated with ointments or plasters of the mercurials or quicksilver. Death by calomel poisoning was particularly unpleasant. Teething powder containing calomel wasn't banned in the UK until after I was born. At that time 10% of babies whose mothers administered the teething powder were killed by it.
The cure for arsenic poisoning was more arsenic. Before Silent Spring makes for an interesting read:
The author doesn't confine himself to the use of arsenic in agriculture; he provides a comprehensive account of its widespread and often injudicious use by the medical profession.