Well, if we think that, then we have seriously overestimated people in general.
We must remember that we are flawed in our perceptions. Biases can only be addressed if they are acknowledged.
To many of these folks, where science or medicine is nowhere near their expertise, "placebo" would merely be a the name of a band.
I'm going to go with the term "Woo" coined at the blogs from badscienceblogs as my reference to all these unproven practices to simplify stuff.
As a reference, woo for me generally covers thing like : energy pendants and trinkets, magnetic fuel savers, unproven health drinks, detoxification(nutritional), homeopathy, acupuncture, electronic car rust protection etc etc etc.
So you can see, woo is a very wide ranging issue. It does not necessarily touch on any field like health and nutrition in particular.
Woo generally tends to have an impact using outlandish claims, and once they have your attention, begin discrediting the other party in order to gain themselves points, or backing their claims with testimonial data. They do this by sounding scientific but not really using proper scientific methods... a "convenient science" if you will.
It is this method which is utilised that we need to understand. The common ground of all things woo: Pseudoscience.