My current job has random drug screenings. We had an anchor go to Haiti, Amsterdam, and Jamaica. Pretty much the 3 drug capitals of the world, all on the same vacation. She was never tested when she came back. I have had to piss twice and really gave them no reason to do so. So I can say it is completely random.
I like the last place I worked. They drug tested you if you were injured only. Save time and money. Where I am now its just a waste of time. Its Broadcasting people, not McDonalds.
I generally don't like them, for example right now I'm sick as a dog and could really use some prescription grade cough syrup. My wife has some codeine cough syrup that she can't take anymore.
God do I want that cough syrup... but I can't because it'll show up on a drug screening.
Not all of us are crack heads, just... sometimes we don't do things quite by the book.