Several people after trying a dose in the recommended safe range and not getting an effect assumed that they needed a larger dose, when in fact the problem was that they did not vaporize the material efficiently the first time. I have already seen more than one intelligent, careful and experienced person accidentally do too large a dose because of this. Fortunately they had sitters and managed to get through the experience safely. It is also important to understand that there have been no toxicological studies of this compound in humans. It is true that the Mazatecs have used the plant for a very long time and don't seem to have problems with it, but when the pure compound is used it would be a simple matter to consume a dose hundreds of times greater than anything ever encountered by the Mazatecs.
Many people consider the effects less manageable and harder to work with than other entheogens.
The majority of people who have had a full blown experience with salvinorin A are reluctant to ever do it again. Anyone choosing to experiment with this compound should always have an alert, clear-thinking sitter present to prevent them from injuring themselves or others. Salvia divinorum as an herb can be used quite safely and many people claim that it has proved beneficial to them. Hopefully there will not be a rush to isolate the pure compound as it is almost inevitable that it will cause problems, people will get hurt, the compound and possibly the plant will get negative attention and it will become scheduled. We will just be adding one more potentially valuable plant ally to the list of species which are already feared and condemned in our society.