But isn't there also the risk that your dog will ignore the shock, not respond as you expect, the collar will fail, etc? When I was doing animal control, we had a lab breeder/trainer who used the e-collars to work his dogs in the park. One day out of the blue, the collar got "stuck" on, shocking non-stop and the dog had an (understandable) meltdown and was shrieking and running though the parking lot. ANYTHING can fail, from your recall command, to an electric collar, to the dog slipping a collar while on leash.
While I respect that their are phenomenal dog owners, here and elsewhere, who take great care of their dogs and love them dearly, and who chose to use the collars, I just couldn't. I'd walk Meg on leash for the rest of her life before I'd shock her. Or just keep doing what I'm doing - training her the best I know how, rewarding her recalls constantly, and taking that chance.