When I graduated college, my first job was working for what was then the Defense Communication Agency (now Defense Information Systems Agency), in a job that required a successful Secure Background Investigation for a TS/SCI clearance, and I was told that the position required a lifestyle polygraph + random urinalysis.

I used this to my advantage on more than one occasion, when the gaming group I was with was a bit too casual with their use of certain recreational pharmaceuticals. I told them straight out that my job required a lifestyle poly and random urinalysis, and that if they decided to do that to me the next morning, then I would be totally giving up my friends to the examiners. That usually convinced them to be more careful.

Strangely, the government never actually gave me a polygraph or urinalysis test, ever.