I look at it from the courtroom point of view. Defending yourself in the eyes of the jury after your "big loveable" 150# rottie goes inexplicably berserk is not going to be easy.
For me, that's enough of a reason not to own one, unless I lived on 100 acres with no neighbors and no children.
Hmmmm... perhaps that's part of the problem with today's litigious society - too many people busy looking at it from the almighty courtroom's point of view rather than invoking their God given common sense. Just a theory...