a few years ago I was on a pretty narrow, nicely twisty road and had been following a rather large truck for a few minutes and was getting a bit antsy.
So I moved my bike to the centerline and looked past the truck. Nice, just two oncoming cars and then I can pass!
I wait for the cars to pass by the truck, gun the throttle and am just about to whip out and past the truck ... when I see the third car that I had overlooked.
If that car had just been twenty meters or so farther back I would have slammed into it head on without even the chance to brake.