The snake oil peddler became a stock character in Western movies: a travelling "doctor" with dubious credentials, selling some medicine (such as snake oil) with boisterous marketing hype, often supported by pseudo-scientific evidence. To enhance sales, an accomplice in the crowd (a "shill") would often "attest" the value of the product in an effort to provoke buying enthusiasm. The "doctor" would prudently leave town before his customers realized that they had been cheated. This practice is also called "grifting" and its practitioners "grifters".
W. C. Fields portrayed a Western frontier American snake oil salesman in Poppy (1936), complete with crowd accomplice. His demonstration (transparently fraudulent?to the movie audience) from the back of a buckboard of a miraculous cure for hoarseness ignited a comic purchasing frenzy.
English musician and comedy writer Vivian Stanshall satirised a miracle cosmetic as "Rillago?the great ape repellent" and many of J. B. Morton's Beachcomber books and radio programmes included short spoof advertisements for "Snibbo" a fictional treatment allegedly tackling various unlikely human conditions.
The practice of selling dubious remedies for real (or imagined) ailments still occurs today, albeit with some updated marketing techniques. Claims of 'cures' for chronic diseases (for example, diabetes mellitus) for which there are only symptomatic treatments available from "mainstream" medicine are especially common. The term snake oil peddling is used as a derogatory term to describe such practices.
http://en.wikipedia.org/wiki/Snake_oil