Here is the standard post, thought I'd help get it out of the way:
WHERE THE HELL WERE THE PARENTS!??!? *arrggghhh!*
If you're going to allow your children to use the Internet, understand that its misuse has the potential to cause serious psychological trauma. If your child is pre-disposed to suicidal thoughts to begin with, allowing unsupervised access to the Internet is potentially dangerous. Kind of like leaving your loaded gun within reach. What were the guardian's of this girl doing after the repeated harassment and torment caused by these kids?
Yes, the kids should not have done it. They now will face the consequences.
Yes, the teachers should have stopped it. Too bad nothing will happen to them. We wouldn't want to make the teachers responsible for anything.
However, the people with the ultimate responsibility are the people who brought her in to this world. Don't have kids if you can't be bothered to be responsible enough to do the quite difficult job of being a parent. That job includes engaging your child in regular communication, following up with teachers to know what is going on at school, and knowing what your child is doing (especially on the Internet). The parents will now have to live the rest of their lives asking one of two questions "Why didn't we do something?" or "Who can we blame for this?"