The scariest moment I've had on a motorcycle is when I thought a friend of mine had flown over a cliff behind me and I was sure he was dead.
Mark is fast and we were out "sporting" on a bunch of tiny roads in western Oregon with a couple other friends, on the way to a rally. We emerged from a forest into a huge clear cut area, which gave more forward view, so I shifted into third because I could see the series of esses in front of me open up. There was a cliff on the left side of the road that fell to the valley below.
Mark was right behind me, I could tell he was close because I kept getting flickers in my mirrors from his headlight. The last wiggle of the esses went behind a small bluff to the right, but when I got close I found that it was a 90 degree turn, so I braked hard before it and then leaned hard and gassed it out of it. I immediately realized that there were no more flashes in my mirrors!

I got to the next turn where there was enough room and made a U, rode back up and parked. I could already see the furrow that a cylinder on Mark's R850R had dug in the gravel leading to the edge. There was real horror in the pit of my stomach. It was easily a couple hundred feet to the bottom.
I got off my bike and started to remove my helmet when... Mark scrambled up over the edge of the cliff. I was never so happy to see someone in my life!
It turned out that there was a shelf about a dozen feet down with a bunch of sapling trees growing from it. Mark and the 850 had landed softly in these trees, just missing both a large stump and also a rotting car.
The other two guys caught up to us and then went for help. They returned with a guy with a boom truck. Mark climbed back down and tied off the cable. The bike came up easy and it was lowered to the road. The only damage was to the plastic cowling around the headlight, and was fixed with some duct tape.
RIDE YOUR OWN RIDE.
PS: This, and another experience, convinced Mark to take up vintage racing. Now he's getting podium finishes in the Honda 160 class.