Freud's Psycho-Dynamic Theory

Now, according to the psychoanalytic view, the personality consists of three systems: the id, the ego and the superego. These are names for psychological structures and should not be thought of as manikins that separately operate the personality; ones personality functions as a whole rather than as three discrete segments.

Like it or not, Freudian theory is still a standard for evaluating personality in spite of the limitations. Can you analyze Freud's psycho-dynamic theory in terms of his views of the unconscious mind, the structure of personality, and defense mechanisms? When are these defenses useful, and when are they detrimental?