The internet has always been kind to intentional hoaxsters, fraudsters and quacks(ters) spreading disease and suffering through medical misinformation. Now Facebook and its social media ilk seem to offer different and harder to stop routes for such misinformation to travel, though as with a lot of social media wossnames, these are probably just online mirrors of existing offline behaviour. What's new is the speed, ease and extent of the spread.
For years, I've seen two different phenomena. The first, smaller and probably less pernicious, is the advice solicitation. Someone's got a funny ringing in their squeedly-spooch, and they want it to be better without the effort of seeing a doctor, spending money or putting pants on, so they ask their online friends for suggestions. This then leads to a flood of people reporting how their aunt's dog's previous owner's cousin's gardener had the same thing, rubbed a cat on his head, and all was well. In short, instead of telling the 'patient' to stop wasting everyone's time and either see a doctor or quit whining, every junk panacea already in that social circle gets a chance to air itself, misinforming not only the original complainer, but also any unsuspecting passers-by who happen to read it all.
The second is worse for society at large: The repeatedly-shared post, expounding on some quack theory or treatment. For whatever reasons (I'm willing to believe it's mostly with good intentions), people like to pass around warnings and recommendations from incredibly dubious sources. These are worse because they get spread to a much wider audience, sometimes repeatedly, for much longer periods.
So far, I've dealt with these sorts of posts on an ad hoc basis, digging up the relevant skeptical articles or original research and trying to convince people that claim XYZ is incorrect. I am not a doctor myself, I never offer counter-advice (other than "speak to a qualified doctor about this"), but I do point out clear flaws whenever my bullshit-detector catches something obviously suspect. For those looking for sources of that sort, here's my list of usual first stops:
But I no longer feel this will ever be sufficient. More often than not, I think I'm wasting my time. What we really need is to encourage a taboo against online amateur doctoring. Perhaps my responses in future should be "you're wrong, here's why, but more importantly, stop posting things like this at all." How do you get people to accept a taboo like that? I'm not sure, I'm not a social media guru. People get weird about expert knowledge (especially when they lack it themselves) and they get weird about their health (for obvious reasons of personal comfort and survival).
I think a good start would be getting as many people as possible to swat these sorts of posts down whenever they pop up with a brief, clear "You are not a doctor, don't pretend you are." Hopefully enough of that will put some sort of dent in the habit.
* Title may be revised on a case-by-case basis upon presentation of appropriate qualifications. Alt-med "doctors" need not apply.