I had a passenger use one, once. It was a girl I was friends with, and her dad wanted to come too, so she was sitting in the back, and her dad was in the front. Before we left for the airport I had given her a bag, and she asked "what's this for?" and I said "in case you get sick."
She said in a matter-of-fact tone of voice, "I don't get sick!"
It was hot and bumpy that day, and on base when we were landing, it started and continued until touchdown. I felt bad, and as we were taxiing back her dad starting laughing at her, but she said she felt better.
From then on I gave all my passengers at least a half Dramamine tablet!