You don't get a haircut from a barber who practices evidence-based barbering.
That's not exactly 100.00% true -- I once overheard a barber priding himself with the fact that someone once got laid the night after getting a haircut from him.
Jokes aside, barbering is evidence-based -- given that it works at all, then barbers either have knowledge of how to do that hard-coded in their DNA (unlikely) or have learned to do that -- using evidence (even though not in a systematized way). You can immediately see that if you use this cutting technique then your client's hair will look this way. OTOH, a practitioner of non-evidence-based medicine cannot immediately see that giving a patient this substance diluted in 10^20 times as much water or sticking a needle in this particular spot or whatever will help cure the patient. (Likewise, musicians are normally evidence-based musicians to some extent, but astrologists are not evidence-based astrologists; can you find more examples?)
OTOH, a practitioner of non-evidence-based medicine cannot immediately see that giving a patient this substance diluted in 10^20 times as much water or sticking a needle in this particular spot or whatever will help cure the patient.
That's wrong. If a acupuncturist puts needles in 10 people and 5 of them lose their back pain than he has "unsystematic clinical experience" that provides evidence for his treatment.
The core of evidence-based medicine is the belief that you shouldn't use that kind of evidence for clinical decision making but that...
In a world where 85% of doctors can't solve simple Bayesian word problems...
In a world where only 20.9% of reported results that a pharmaceutical company tries to investigate for development purposes, fully replicate...
In a world where "p-values" are anything the author wants them to be...
...and where there are all sorts of amazing technologies and techniques which nobody at your hospital has ever heard of...
...there's also MetaMed. Instead of just having “evidence-based medicine” in journals that doctors don't actually read, MetaMed will provide you with actual evidence-based healthcare. Their Chairman and CTO is Jaan Tallinn (cofounder of Skype, major funder of xrisk-related endeavors), one of their major VCs is Peter Thiel (major funder of MIRI), their management includes some names LWers will find familiar, and their researchers know math and stats and in many cases have also read LessWrong. If you have a sufficiently serious problem and can afford their service, MetaMed will (a) put someone on reading the relevant research literature who understands real statistics and can tell whether the paper is trustworthy; and (b) refer you to a cooperative doctor in their network who can carry out the therapies they find.
MetaMed was partially inspired by the case of a woman who had her fingertip chopped off, was told by the hospital that she was screwed, and then read through an awful lot of literature on her own until she found someone working on an advanced regenerative therapy that let her actually grow the fingertip back. The idea behind MetaMed isn't just that they will scour the literature to find how the best experimentally supported treatment differs from the average wisdom - people who regularly read LW will be aware that this is often a pretty large divergence - but that they will also look for this sort of very recent technology that most hospitals won't have heard about.
This is a new service and it has to interact with the existing medical system, so they are currently expensive, starting at $5,000 for a research report. (Keeping in mind that a basic report involves a lot of work by people who must be good at math.) If you have a sick friend who can afford it - especially if the regular system is failing them, and they want (or you want) their next step to be more science instead of "alternative medicine" or whatever - please do refer them to MetaMed immediately. We can’t all have nice things like this someday unless somebody pays for it while it’s still new and expensive. And the regular healthcare system really is bad enough at science (especially in the US, but science is difficult everywhere) that there's no point in condemning anyone to it when they can afford better.
I also got my hands on a copy of MetaMed's standard list of citations that they use to support points to reporters. What follows isn't nearly everything on MetaMed's list, just the items I found most interesting.
90% of preclinical cancer studies could not be replicated:
http://www.nature.com/nature/journal/v483/n7391/full/483531a.html