Well, I've been blessed with a very strong resistance to addictive behavior (with everything), but I can certainly see how many could get hooked rather quickly. I really don't do it often at all anymore, but if some just HAPPENS to be around and I do partake, I definitely don't do it again for at least two months. It's when people begin to do it frequently (and that doesn't neccessarily mean everyday) that they quickly get into trouble. Definitely depends on the person and the environment they are in (repeated exposure, etc.). Not a healthy thing by any means though!
And in regards to the drug test, definitely ~10 days, and if they are doing a hair test (high security or some casino jobs), then you are screwed.