Just wanted to say I've really enjoyed reading this thread!
Back in 2005/2006 I wrote my social anthropology dissertation on the uses of complementary therapies in the context of UK palliative care services (I was working in a hospice at the time which used a lot of complementary treatments for it's patients, to alleviate pain and stress and improve quality of life).
Whilst mine was not an empirical based study (I was conducting ethnographic research) I had the chance to read a lot of the available empirical papers, the arguments against and counter-arguments etc and found the contentions between the medical professions and complementary/alternative medicine really fascinating.
I am a bit rusty, but I remember some studies identifying different factors which play a role in placebo responses, the response is very subjective and depends upon a number of variables so it's very, very difficult to isolate these in clinical trials especially in complementary medicine... from what I understand, randomised controlled trials used to test drugs are designed to eliminate subjective variables and 'placebo' responses to prove it is the drug creating the healing effects and nothing else, however in complementary medicine it is these subjective variables which will have an impact on the efficacy of a 'placebo' response and therefore could impact on the results of treatment if treatment relies on subjective variables (this of course depends on your view of 'placebo' responses and how much a part they play in any given therapy). It's not impossible to empirically test, but it is difficult to produce results that will not be questioned by the scientific community. I would also like to see more study go into unravelling the 'placebo' effect itself, as it is quite effective and can often even be improved by manipulating the variables to suit the person being treated.
On another note, I agree with the post above that mentioned the apparent scepticism and animosity of medical professionals being linked to ethics in medicine. I remember one quote by a doctor in response to a study on the impact of positive thought on breast cancer survival rates (I think the study was by Spiegel et al, it was a very sound preliminary research paper from what i could see). This doctor argued about how we only ever say these things in connection to diseases that we do not understand, or that have no cure or clear pathology.... she was saying something like "well we do not say we can 'think' ourselves better when we have illnesses like syphillis or tubercolosis, with clear causes that we understand".
There are other issues raised by medical professions too regarding the raising of false hopes of a cure, that patients might be led to reject tried and tested medicines that are proven to work.... also ethical issues with providing a 'treatment' that they know has no actual 'effect' in itself as such although the patient is told it will have an effect (interestingly, some countries do have medical professionals who will try using placebo 'sugar' pills quite frequently to treat minor ailments but I think this is not the case in the UK... also interesting how homeopathy is quite highly regarded by medical professionals in Germany although other countries will reject the same evidence of it's efficacy).
It was very interesting conducting anthropological research into these issues. Anthropology by it's nature rejects the idea that everything can be tested empirically... empirical testing is good and important, but in Anthropology it is just a small part of the bigger picture because in anthropology the world ceases to be an objective place! So my own study was more focused on the attitudes, beliefs and values of patients and professionals in the Hospice context and not so much looking for 'proof' that therapies worked, it was more focused on the uses of the therapies in the context of treating people with medical conditions that were terminal and unlikely to improve.
Anyway, my rambling's over...