I would think that suffocation would be the cause of death for anything swallowed whole. Faster than digestion, but still not a very nice way to go.
Although this video is facinating there's really no excuse for using live goldfish in this way. Especially with a species that will apparently attempt to swallow anything new in the tank, including rocks!
Dead food would still be taken eagerly.
I know it's nature an all but it's a bit up setting for me to think that people want to watch this kind of thing, that fish is awsome but there are some fish that are good to keep in an aquarium and others that are just meant to be left in the wild.