The ignition key cylinder on my car (and apparently many other GM models) is of very poor quality. No way should an ignition lock completely fail on a car with only 40K miles. This is clearly a defective part/design that should be recalled and rectified by GM.

I have several much older vehicles and have never come across such an insidious and totally disabling failure of what should be one of the simplest and most reliable parts of any vehicle. This is surely a safety issue as well - I'm lucky it happened to me during the daytime, in a safe urban area and in good weather.

Update from Sep 15, 2009: The only way to drive the car (and avoid a tow) was to drill out the ignition cylinder.