Why? What do they get out of it?

Recently my English teacher gave my class an assignment. We had to write about the positive and negative factors of social networking sites. We also had to research one negative story involving various social networking sites.
My research lead me to the very publised case of Pheobe Prince, a fiftenn year old girl who hanged herself after months of bullying. I wont go into detail on the case. If you wish to know more simply search Pheobe Prince on google. I was appalled whe I read the details of her bullying and it begs the question "why would someone want to do that to another human being?" No one should be treated this way because of who they used to date, where they come from. They should be treated because of the things they do.
Bullying is a serious issue and is present in every school. Some schools have a more serious case of bullying. Social networking sites seem to make bullying easier as they can simply delete their comments and pretend they didnt do anything.
Anyone who bullies someone so much that they end up commiting suicide should be charged no matter what their age! They should have to face the consequences of their actions!