You is silly. ;p
There are a good handful of chemicals/compounds that are like that. To change one molecule or the shape of a certain compound can alter some of the properties slightly or significantly. Also happens with the removal or addition of molecules/compounds.
A few compounds can be completely harmless but if the molecules are arranged differently in structure, deadly. Isomers I think (thanks google ;p). Please correct me if my chemistry information is wrong (it has been years since I have taken a class).
So ya, hopefully the stuff given at the clinics is the right stuff. There have been cases of malpractice where false doctors were giving people fake botox injections. Now that could be scary going into a place with unliscensed staff and not even knowing it. e.e
There are also creams and other cosmetic products out on the market to "help" and "make" people feel and look younger. The chemicals in the products that focuses towards enhancing lips contains some skin irritants, thus fuller lips guaranteed for some period of time. Not every over the counter cosmetic item is necessarily safe either.
As long as people have a self-image of themselves as "ugly" and strive to make themselves feel good; there will be open markets for things such as botox, makeup, cosmetics, cosmetic plastic surgery, etc. Chances are those markets will not be diminshing anytime soon.