http://news.yahoo.com/s/nm/20081215/us_nm/us_cocacola
Stevia isn’t approved as a food additive in the US despite being used safely elsewhere for decades. I’ve heard (no cite) that it’s essentially the influence of Big Artificial Sweetener over the FDA that has kept it from getting approved.
You could get it as a dietary suppliment to use for your own purposes, but I’d be glad to see become a food additive and make it into mainstream products. It often tastes better (at least to me) and is possibly healthier than the current alternatives.