The morals/lessons to learn from these stories aren't always obvious, and I'm not sure it's my job, or that I'm "qualified" to try to bring them out. Certainly I'm not trying to add morals to the stories as I'm told them.
However, one lesson to learn from the story at http://news.ycombinator.com/item?id=994358 might be that "proving" and "testing" your code only goes so far. In the end, there will be failure modes you haven't anticipated, and fools/users who are more ingenious than you expected.
Perhaps a lesson to learn from this story is that documentation is good, but it's never enough.
I'd be interested to hear of other people's takes on this.