What is the point of Trolling?

Anyone who has ever been on a networking site, or message board, has come across at least one Troll at some time or another.  The question that really bugs me is, 'What is the point?'  Why do these people feel the need to post offensive comments, especially about people that they don't even know.  What are these so called people trying to achieve?  Are their lives so empty, that they have to incite anger and hate in order to get themselves noticed.  DO NOT RESPOND TO THESE PEOPLE.  Just report and ignore.  They obviously lead very lonely lives, and have enemies where most people have friends.  DO NOT waste your time arguing with Trolls.  If they start a negative argument, respond with a positive one.  The world would be a much better place, if we could all learn to spread love and not hate.