" ... the over-use of parodies, assuming and depending on knowledge of the original as it does, might put off new entrants to the world of folk, because they are little more than an "in" joke that could create an air of exclusion."

I'm with you on that, George. I wouldn't be without them, though. It just takes care in timing their use. Possibly the best time for a parody in a group with a number of new people is immediately after the original - and it's just too bad if the singer of the original gets upset.

Another thing I have noticed with parodies - no matter how worn out the original, the parody tends to wear out even more quickly with over-use.