While I agree that a shotgun can be quite effective for self-defense, it still needs to be aimed to a degree. At close quarters (i.e., in your house), the pattern for 00 buckshot is typically only a few inches wide, much smaller than a torso, doorway, or the "broad side of a barn." The longer barrel relative to a handgun will aid in an instinctive shot without precise aiming down the barrel, but to just "point and shoot" is a bold move when firing a round capable of penetrating several walls.there is no better defense gun then a shotgun. just point and shoot, no more bad guy.
EDIT:
And see pernox's well timed post below. Right on.