I have seen this method used. It works pretty well, but is REALLY DANGEROUS!!!! Just think about what you're actually doing, first of all, you've produced a homemade shotgun, you never know if it'll blow up or not, secondly, you've loaded this gun taken it out into the world and left it with the safety off. Other than that, I've always known them to be really effective, except that you'll shoot several coons, or rabbits or other game that you didn't want b/c they will be curious and come up and sniff around, if your "trigger pull" is too light, then that'll set off the shell at something you don't want. Then you usually loose the bait meat that you had b/c yotes will come eat it after the shot.
IMHO they aren't a good idea, unless you sit a long ways off and watch them the whole time, just like if you were calling normally.