Keep in mind that unless that stranger specifically OKs you riding in his draft, he has absolutely no obligation to ride smoothly, nicely or with your safety in mind. I haven't looked at the laws of other states, but Oregon subjects bikes to the same laws and obligations as cars with specific exceptions. Tailgating is not one of them. A judge is going to have little sympathy if he hears you were operating your vehicle 24" behind another.

And as a fix gear rider, I really don't like others drafting me without telling me. I've ridden fix gears for decades. It's like walking. If I am approaching a turn, I know I have to hit the apex slower than a geared bike so I don't scrape the pedal. So I often simple do a quick back-pressure on a pedal stroke. Bleeds just enough speed to keep my pedal off the pavement if I am not going too fast. Now I never do this riding in company. But alone? It's fun. Years ago I was riding through a park in Seattle on my early season commute. Did this going into a right angle turn on the path and heard a huge commotion behind me. The rider I had seen oh, 50 yards back had caught up and was drafting me. He didn't crash, but his serenity was blown out of the water. Now in Portland, I am waiting for the day when a brakeless fixie does this and I hit the brakes. I'm hoping I don't crash. They certainly will.

Ben