It can happen very easily, although it usually doesn't cause damage as severe as this. If a hook pulls with a fish facing any direction other than straight at the rod, the hook has a chance of hooking another part of the fish.
Unless rules dictate otherwise, I always use a barbed hook. Barbless hooks can move during the fight creating larger holes in a fishes mouth, where as a barbed hook will lock in place and won't slip. The only danger a barbed hook poses to excess mouth damage is when they are being used by anglers that don't know how to remove them.