One time I was riding down a curvy road that is frequented by weekend warriors. All the cops were in town at some parade so I was very liberal with the throttle and eventually came up behind a naked sport bike rider. I wasn't even close to tailgating him but when he saw me in his mirrors he turned his head around and gave me a little glance as if to say "please". Then he accelerated like a bat out of hell from the 65 MPH we were going to probably closer to 100. He quickly left my line of sight around a few corners.
I caught up with him a few minutes later...he was in a ditch, his bike was fairly undamaged because the ditch was full of tall grass and it looked like he just over-shot a corner..but he was confused as all hell despite looking uninjured. I wasn't going to try to convince him to take his gear off so we could inspect his injuries (I'm no EMT) but I tried to get him to wait for an ambulance or a ride home. He refused to give me consent to call an ambulance and refused to call anyone to come pick him up. He was walking and talking fine albeit a little slow. But once me and another rider who came along picked up his bike and put it near the road, he got on it and rode off grass stuck in the countersprocket cover and all. He swore he was fine but to this day I have no idea what happened to him. It looked like he may have hit a boulder or two placed in the ditch (it was more or less someone's front yard) but he said he didn't. Oh well, to each their own. I don't think he ever said thank you once.