You know what fascinates me and strikes me as ironic about this incident as well as my own near-disaster is that these were both cases of metal alloy stems failing. I have always done tons of climbing and I'd have to say that I put considerable stress on my stems/bars because I'm often out of the saddle and moving the bike around to get up some pretty severe gradients. In my case, I was then riding a friend's old bike, but the stem was actually pretty new (it was a Cinelli quill stem; metal alloy).

I currently have two carbon fiber bikes and both have carbon fiber stems as well (and bars). I always look at them with suspicion when I ride, yet put my full trust in them. Or, better stated, I put potential problems out of my mind. Nothing has happened yet and hopefully nothing will.