While measuring the current at the circuit box for the posting above, I noticed that one of my 20a breakers has a #14 wire attached to it. The only thing on the circuit is a refrigerator that draws 7a to start and 1a to run.
As a practical matter, just how dangerous is this? The only outlet on the circuit is in a position where it could not possibly be used for something else by accident, so the only problem would be some weird overcurrent of more than 15a and less than 20a in the refrigerator; and that just doesn't seem likely.
It would require replacing a double breaker, so it would be about $10. Yes, I realize that is cheaper than replacing the house.