How is the theme of broken dreams explored and developed in the novel Of Mice and Men?

The characters in Of Mice and Men
find themselves in a hopeless situation of drudgery and insecurity.  They work temporary
migrant jobs, and can be fired at any time.  They live from payday to payday, a hand to
mouth existence.  This is true of Lennie and George, the main characters, but also of
most of the rest of the people in the story.  Remember that it takes place during the
Great Depression, a time of mass unemployment and even
starvation.

So the dream is developed as a way out of this
life.  Lennie and George find they can, with Candy's help, buy a little farm from a
couple that's broke.  They can grow their own food, be safe from firings, and live with
just a little security.  Candy doesn't have to worry, as a physically handicapped senior
citizen, where his next meal is coming from.  He has a place to stay and a place to die
comfortably.  Lennie gets to tend the rabbits.  George can stay in one place and start a
life.

The dream is inevitably broken.  Lennie kills
Curley's wife and the whole plan falls to pieces, just as it is about to be realized. 
Multiply this broken dream by hundreds of thousands and you have the social misery that
was the Great Depression. 

P.S.  You might also add the
dream of Curley's wife, to be in the pictures in Hollywood, crushed by the reality of
small town farm life in the Depression, and an unhappy marriage.