How bad is bullying?

Bullying in schools and the internet is getting so bad that the President of the U.S. needed to address this issue.  He talks about how so many are getting tormented and are feeling so depressed that they are committing suicide.  This is so sad and he is stating how he wants to put an end to this type of harrassment; because he himseld was bullied growing up and he felt the same way that many of our teens do today.  We have all gone through the stage of being bullied or have been the bully, and now looking back on those times I wonder why do people do it?