LWN reports (subscription required) on the hazards of proprietary software. They present a great case from a Wired news article of a robotic parking garage in Hoboken, New Jersey. Here is the (somewhat shortened) gist of the story:

The company which owns said software, decided that the time had come to raise its rates. The city disagreed, and talks between the two came to an ugly point. Once the old contract ran out, the garage was no longer operable and hundreds of cars were left imprisoned inside. Robotic Parking Systems claimed that any attempt to operate the garage constituted copyright infringement, since the city no longer had a license to run the required software.