Jeez, best post so far is from GSD's!
My initial reaction to looking at a photo of a prong collar is to go 'whoa shit, WTF is that? Nasty stuff!'
My 2nd reaction is to ask myself am I being a hypocrit with my 1st reaction?
I have used check chains in the past. As a matter of fact, my father's dogs in NZ used nothing else BUT check chains. That's the way it was; that was their understanding at that time/era. They didn't consider anything else.
I will no longer use a chain-link check chain, however, I will use a nylon check chain if need be.
My reason for not using chain ones is this: I have seen too many dogs which have medium to long coats get fur caught in them. I have seen too many dogs who have been uncomfortable (naturally) from the heat that a check chain can radiate. Try leaving one sitting in the sun for a few minutes, they DO heat up fast. Now put it around your neck, and you might understand where I'm coming from.
If you don't understand, that is your perogative - the above opinion is mine.
Nylon check chains in my experience do not cause either of the above, and I have over the years had immense success with them.
I have not needed to use them on every dog I've ever had. Most I have not needed them, but some - yes my oath I have resorted to them to train them to heel correctly. With those dogs, nothing else had worked - things that had been successful with other dogs just didn't sink in no matter how much I trained or perservered.
I guess what I'm trying to say in my long-winded way (yes, I'm aware I'd give 'Gone with the Wind' a run for it's money ) is that what works for one doesn't neccessarily work for another. All dogs are different; all humans are different; each dog's job/purpose is different.