If anyone's at all interested in risk analysis or robust software, it's totally worth finding a decent writeup on the Ariane 5 failure --- it's a fascinating postmortem in just how many unexpected little things together added up to a big boom.

Everything is incredibly obvious in hindsight, of course, but making things obvious is largely what hindsight is for.

And once you've finished reading that, go look up the Therac-25...