I've read three stories in the past 2 weeks or so about young people, aged 13-15, taking their own lives apparently due to online bullying on sites like, well, I'm not going to name any of them.
I can only say, that if this is happening to you, that you please get help, talk to someone - a family member, teacher, school guidance counsellor, Childline, the Samaritans...
We all know how addictive the web can be, how it can be hard to stay away from sites we like, but it is not worth suffering in silence to the point where you are harming yourself or want to end things. There is help if you need it.
If you are a parent, don't have the family PC in the child's room and please talk to them about the internet.