In chapter 6, what is the significance of Lennie's dream about Aunt Clara and the rabbit?

In Chapter 6 of Of Mice and Men,
Steinbeck uses the dream sequence to give Lennie some depth of character.  The dream
functions as a kind of soliloquy, for the reader could not know what Lennie is thinking
otherwise.

The dream presents Lennie's great fears: first
disappointing Clara and George and then being abandoned by them.  Clara turns into a
giant rabbit and tells Lennie that he isn't worthy to tend them on the dream ranch.  The
rabbit also tells him that George is going to hurt and leave him.  All of this, more or
less, will come true.

The rabbit is an example of
Steinbeck's anthropomorphism (attributing human qualities to an animal).  It is
obviously an omen that foreshadows Lennie's death.  He almost sees it coming, though he
never suspects it when awake.  The rabbit is a symbol that the American dream is an
illusion, that it is destined to tempt guys like George and Lennie.  Subconsciously they
know that the dream ranch was only a romantic ideal; it could never have worked
out.