No clear-cut distinction can be drawn between professional and amateurs in science: exceptions can be found to any rule. Nevertheless, the word "amateur" does carry a connotation that person concerned is not fully integrated into the scientific community and, in particular, may not share its values.
Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes, that together determine what shall be produced and how resources are used to produce it.
While warnings are often appropriate and necessary--the dangers of drug interactions, for example--and many are required by state or federal regulations, it isn't clear that they actually protect the manufacturers and sellers from liability if a customer is injured.
