Who is the responsible party?

Object Oriented design is all about placing behavior and data together, of making the object responsible for its own operations. The problem then becomes identifying which object is responsible for what. This is usually pretty easy, since the natural owner of an operation is usually clear. Note that I don’t much care for the choice people make between things like parent.AddChild(child) vs. child.AddTo(parent). Both are equally good from my point of view. What I don’t want to see is this: