When the company I work for recently needed a number of us to undergo drug testing to land a big contract, I discovered that my boss and a number of folks on my team were regular MJ smokers. The company we were contracting with didn't specify the testing methodology that was to be used, so my boss picked the one with the shortest detection window -- two days for the saliva test.
I really would not have suspected that any of these folks were pot smokers, they're all very professional and do not fall into any of the stereotypes you might expect. I myself smoke 3-4 times a week, usually on the weekends.