A first hand experience tells me that, at least in the case of Fords, keys are still somewhat generic. Not too long ago, I owned a ‘91 Ford Escort wagon (not exactly stylin’ but I was a poor college student at the time). At the same time, my father owned a '91 Escort GT (the sport model). Each car had one key that did everything; doors, trunk ignition. Out of curiosity, I tried my key in the locks on his car and found that while it would not open the doors, it did work in the ignition switch! Draw your own conclusions.
[[I tried my key in the locks on his car and found that while it would not open the doors, it did work in the ignition switch! Draw your own conclusions.]]
My conclusion would be that the ignition is worn out and less sensitive than it was. And the link to the Staff Report is: http://www.straightdope.com/mailbag/mcarkey.html