CarbonKyle, scourge of alternative medicine and pseudoscience of all sorts, has some negative things to say about placebos in the comments here. As a frequent user of what one might term semi-placebos (things I hope will help a little, but are primarily recommended to give a non-harmful treatment whilst the body heals itself) I felt I had to speak up for the humble placebo:
I recommend "The House of God" for a medical perspective on the value of, as Shem puts it "Doing as much nothing as possible."
Allopathic medicine prescribes a lot of ineffective or unnecessary medicine -- these are really placebos by another name. The difference is that while a good placebo is harmless, a bad placebo -- like an antibiotic for a viral pharyngitis or a muscle relaxant for back pain, or (a horror that takes place 250k times a year in the US) an unnecessary heart cath for stable angina -- may have some serious negative health consequences.
Placebos are necessary because treatment is part of the ritual of healthcare. Listening, helping the patient make sense of the problem, and offering treatment all have a value in themselves, apart from the biomechanical efficacy of the treatment (or even whether the diagnosis is correct.)
It's true that many people find the explicit use of placebos unethical, and it may be. But if you were to ask a hundred doctors "Have you ever prescribed a treatment you didn't believe would cure the patient, in order to give a patient something, knowing that the disease was going to get better in time regardless?" 90% of them would say yes (and the other 10% are lying.)
The physician has a different role than the scientist. The purpose of the scientist is to seek empirical truth; the purpose of the physician is to seek healing. And to do that, our mandate is broad:
"Life is short, and Art long; the crisis fleeting; experience perilous, and decision difficult. The physician must not only be prepared to do what is right himself, but also to make the patient, the attendants, and external circumstances cooperate."