People Change But Seldom Do...Do Bully's?!

So I was watching The Big Bang Theory last night and to my surprise the episode was about facing your bully as an adult.  In the episode the bully of the past reverted back to old habbits of bullying which in the world of tv sitcoms proved to be a perfect plot for humor...but the fact that in real life former bullys do walk among us makes for a stark reality.  What happens to bullys of the past.  Do most of them have epihonys and realize the wrong they have done or do old habbits die hard.  Afterall, the old addage saying "people change and seldom do".  If that is the case, how are these former bully's integrated into society, are they still causing pain in others lives?  Which reminds me of another funny show, Will and Grace, where Will's former bully tormented him in the work place in the same sadistic way he did when they were on the playground.  I am going to focus my weekend research around the notion of what becomes of bullys.