This mildly prosaic retelling of the Therac-25 incident is worth a read. The source is definitely going on my reading list—I've heard and read about Therac-25 on multiple occasions, but hadn't yet gotten to this, even though it's the first reference of the Wikipedia article.

Sidenote: pictures like this of the radiotherapy machine going all swivel-like make me really uncomfortable. Is there a name for the fear of tall, heavy things tipping over?

(Via Lobste.rs)