[tuxmentat]

Actually, I find that ironically the cars is probably the most readily understood complex machine out there - at least here in US. Most people have very good grasp on the basic principles, usage and surprisingly in-depth knowledge of the internal workings of the vehicle. For example you can say something like "I'm having issues with my transmission" and most people (including those who don't drive or own cars) will have a pretty good idea of what you are talking about, what the symptoms are like and even where you can go to get it repaired and how long it may take and how much money it may cost.

The simple fact that we frequently use car analogy to explain complex computer concepts just helps to reinforce this notion.