Medicine that doesn't work -- acupuncture and acupressure

Practice: Acupressure

In 15 words or less: Pressing on specific spots on the body stimulates healing.

Initial reaction: Seems pretty unlikely.

What it really is: In traditional Chinese medicine, they believed that the body was animated by a magical force (or energy?) called chi. There's something to do with yin and yang there, too, but it's all pretty self-contradictory. Anyway, the idea is that disease is caused by an unbalancing of yin and yang, possibly caused by an obstructed flow of chi. Manipulating certain points on the body redirects the flow of chi, curing ailments.

In acupuncture, you stick needles into the points to change the flow of chi.

In acupressure, you rub the points using one of about a dozen techniques. There are special wooden balls, or you can use your fingers, or your thumbs, or a martial artist with a 12th degree black belt can poke you and you'll die 3 days later from chi disruption.... (A similar thing led to a great storyline in Ranma 1/2, however, so I guess the practice isn't totally worthless.)

Occasionally, a small electrical current is applied to inserted needles. That does have a sort of plausible mechanism for doing things locally, but even then, it doesn't work as claimed by practioners.

Why they still say it works: No one can seem to give a good reason. It's a "prescientific" system, which I guess exempts it from having to actually work? The only even slightly possible reason I've ever heard is that it stimulates blood flow. But in that case, the specific points shouldn't matter, right? And going for a quick jog should, by that logic, cure even the most horrible diseases.

Why it doesn't work: There's no reason for it to work. You're not animated by magic. This might have been acceptable thinking 2000 years ago, but now? Get with the times.

Practitioners can't even agree on where the needles should go, or where they should rub. They don't agree for which conditions it might work. They don't agree on... well, on anything. That alone should indicate that it's a big sham.

A number of recent studies on a variety of conditions (arthritic pain, repetitive motion stream, for example) have showed that acupuncture with fake needles is no more effective than acupuncture with real needles.

The existence of chi points is resoundingly ruled out by other studies, which found that it doesn't work for back pain or nausea, either.

That's not to say there there is no effect. Of course there is the placebo effect... but fortunately, that works even if you tell the patient that you're using a placebo. There's no need to stick needles into people and risk infection, and there's definitely no need to pretend you know something about medicine when all you're doing is giving a glorified massage.

Resources: More information than you could ever want is at Skepdic.