Depending on the company I suppose. I believe if your not a chronic smoker and in good shape, don't let randoms scare you. The company i worked for said they did randoms, and I was there for 5 years and never gotten one. I usually asked co-workers about it and they were like, if you walking into walls or falling asleep at ya desk (or any weird suspicious activities), then you may get red-dotted to do a random drug test.

Another instance that happen was that one day they found someone pipe in the men bathroom, so they tried to give all the men random drug tests. They couldn't because 1. it was a public bathroom, anyone can use it. 2. Against Union contract.