ALL THE TIME!!!
Like others have said, I get my number first, then shop. Makes for some pretty snide comments from others when I finally belly up to the cutting counter with my bolts. They didn't see me get my number, which is in my pocket, and they are quite rude with their comments when they inform me that I have to go to the back of the line and take a number. I simply smile sweetly and pull my number out of my pocket. Heh.
I've discovered that if I shop around 8 pm, the store is usually pretty quiet. And I NEVER go on weekends.