Have been drafted by folks I don't know, and I have (on rare occasions) also drafted folks I don't know. I try not to make a habit of it. Fact is, when you have no idea who the person is, it's even money that person has no clue how to ride in train. Have had someone once ride far too close to my rear wheel, and it ended badly for him. Wouldn't be my preference to allow an unknown to do that. Would be less reticent if the person first sprung up a discussion and we later agreed to do it. Depends.