So what ?

This has been a very common expression i get from many people, SO WHAT? It has become very common to say, So What? What happens if i do this or i say this... haha!! So what ? I have no empirical evidences to tell what happens when you do something. If i start doing that...It can be a hilarious game ever. Anyways so far nothing happens, when it happens to you...you will know. Then when people will say, So what?? That day you will know it really mattered to someone somewhere, it has affected someone somewhere and it has hurt someone somewhere............ SO WHAT?