So, here is the scoop. Why have we not seen stevia for sale in the U.S.A. until the last few years? It was banned by the FDA until 2006. It still can not be used in products as a sweetener; like in a soft drink. But, it can be sold as a powder form to put into coffee, tea, etc. Research in 1999 found that stevia carries some form of carcinogens, and therefore is deemed unsafe in large quantities.
It has been used in tropical areas in South America for decades or even centuries. In Peru stevia was used to sweeten the local Yerba Mata drink. The plant is best used in modern day for the diabetic. It is sweeter than sucrose, but has no effect on blood glucose.