Then there is the pure "I'm stupid" syndrome. As I pointed out on the other board, the NCAA had two "leaving early"(lost contact with base) calls in the last three years, one of them being the final out of the championship game when the runner thought the ball was loose when the pitcher was just standing in the circle with it.
The other was a couple of years ago when a runner for a CA team (UCLA, I think) just walked off 3B to kick a small stone out of the base path.
And as I discovered this past year, it isn't just in FP either