I was going pretty fast down a very steep gravel drive I usually ride up to get to the park. I figured I'd be ok because I knew the road and I was watching for vehicles, but I hit about 3" of gravel on a corner. My front went down, my back went up and I remember trying roll at the same time as I was trying to soften my bikes landing with my feet. My bike was smart enough to land derailer side up, but the seat got scuffed up
Actually, given that there was only superficial damage to the bike and my legs, the overall experience was kinda fun, but I don't plan on doing that on a regular basis.