Maybe some of those 5 would have lost their pain even without needles

Right, that's why it's unsystematic.

In the Bayesian sense of the word, "I stuck a needle in this person and the amount of pain he reported went down" would have to be considered to be evidence that would increase the Bayesian possibility that your hypothesis that acupuncture helps back pain is correct. However, it's not systematic, scientific evidence. To get that kind of evidence, you would have to do systematic studies of a large number of people, give some of them acupuncture and give some of them asprin, and see what the statistical result is.

I think that's what bogging this discussion down here, is that the word "evidence" is being used in two different ways. If we were perfectly rational beings, we would be able to use either kind of evidence, but the problem is that the first kind of evidence (individual unsystematic personal experiences) tends to be warped by all kinds of biases (selection bias, especially) making it hard to use in any kind of reliable way. You use it if it's all you have, but systematic evidence is very much preferable.

OK, if you consider the point of astrology to be “making money”, as opposed to “predicting people's personalities and future events”

I didn't. I advocated another goal, entertainment. I don't know that much about astrology but I think a fair percentage of the people who do pay a astrologists do it for entertainement purposes.

Letting someone stick needles inside you, when you go to a acupuncturist is less about getting entertainement.

The kind of people who like astrology often also like other personality tests that they find in magazines. People enjoy going through those tests.

If an astrologer would tell people something about their personality that's accurate but that those people aren't willing to accept, I doubt he would stay long in business.

A bit like the musician who only plays music that he himself considers to be good, but that's "too advanced" for his audience. If the musician only sees his own opinion of his work he's not different than an astrologer who only sees whether his horoscope is good. If you call that musician "evidence-based" than the astrologer who goes after his own judgement of his work is also "evidence-based".

But now that Qiaochu_Yuan has made clear that it's not alternative medicine that he was talking about, this is kind of moot, so I'll tap out now.

Why does that matter to the question whether barbers can be meaningfully to be said to practice evidence-based barbering?