I don't agree that once is enough to make you an addict or I would still be using it, it depends on you and your willpower.
It isn't a drug I would recomend to anyone but it is a free choice.
Purity and precise quantities give different results as will any natural tollerance to drugs, keep in mind that a difference of a few percent in purity can be the difference between enough and too much.
Also remember that some unscrupulous dealers "cut" it with some evil shit.