It is interesting reading about the controversy regarding this plant.
One of the interesting notes is that in the early 1900's there was a movement to introduce Stevia to the public at large. Through some of my research, before Stevia marketing started, a dirty little lie was introduced to the public and government by quite possibly 'Big Sugar'. This villianised the plant and as such was in many countries 'Stevia' was considered a controlled substance like cocane. For a time it was even illegal to market a product stating that it is sweet if it did not have sugar as the sweetener. Could it be that the vast profits that Big Sugar is making could have been at risk?
Stevia can be grown by anyone. This topical plant can be grown in northern Canada. This is quite different to sugar cane, sugar beets, corn etc. that sugar can be extacted from. This fact is probably why Big Sugar has lobbied so intensely to limit anything that would cut into their profits. Profit is the name of the game. You piss them off, they come after you.
I my humble opinion there is room for Stevia in the market place on a commercial scale. Sugar is a $178 Billion a year market industry. These are the official numbers. Currently world wide sugar production has plateaued. There is still room for other products in this niche like Stevia.
Final note: I do not think that 'sugar' will ever be fully replaced by other sweeteners. The body requires this substance in some form whether simple or complex to run our bodies but not at the amounts that are put into merchandised product.