Wikipedia on Christian Friedrich Samuel Hahnemann - the inventor of homeopathy:

Hahnemann claimed that the medicine of his time did as much harm as good:

My sense of duty would not easily allow me to treat the unknown pathological state of my suffering brethren with these unknown medicines. The thought of becoming in this way a murderer or malefactor towards the life of my fellow human beings was most terrible to me, so terrible and disturbing that I wholly gave up my practice in the first years of my married life and occupied myself solely with chemistry and writing.[3]

After giving up his practice around 1784, Hahnemann made his living chiefly as a writer and translator, while resolving also to investigate the causes of medicine's alleged errors. While translating William Cullen's A Treatise on the Materia Medica, Hahnemann encountered the claim that cinchona, the bark of a Peruvian tree, was effective in treating malaria because of its astringency. Hahnemann believed that other astringent substances are not effective against malaria and began to research cinchona's effect on the human body by self-application. Noting that the drug induced malaria-like symptoms in himself, he concluded that it would do so in any healthy individual. This led him to postulate a healing principle: "that which can produce a set of symptoms in a healthy individual, can treat a sick individual who is manifesting a similar set of symptoms."[3] This principle, like cures like, became the basis for an approach to medicine which he gave the name homeopathy.

So, homeopathy is based on an idea from a man who thought that medicinal drugs in the late 1700 was potentially harmful. No shit. The understanding of chemistry and medicine is incomparable to today's sciences, the periodic table, a vital part of the basics of chemistry wasn't invented until nearly 100 years later. Belief that this kind of treatment is as effective, if not more than conventional medicine is beyond me.

I'd like to quote Dara Ó Briain "people say 'well, science doesn't know everything' - well science knows it doesn't know everything, otherwise, it would stop."

and

"Well herbal medicine, 'herbal medicine has be around for thousands of years', indeed it has, and the stuff that worked became, medicine"

http://www.videosift.com/video/Dara-O-Briain-on-Homeopaths-and-Nutritionists