Our philosophy around that is to empower people to have the tools to do it themselves, to protect themselves. That's where the protected accounts come in, and the ability to block particular people. You can be anonymous on the service. You can not agree to let other people see your tweets if you're a protected account.
We have resources for teens. If there is harassment targeted at particular individuals, then that's a violation of our rules. We don't allow that if that is brought to our attention.
We also provide resources on our service for parents and teens to help them deal with these kinds of situations. Blocking and ignoring: that's often what we find to be the most effective way to go. Often if you actually ask for content to be taken down, it just makes the person who is the bully feel as though they were successful in what they were trying to accomplish. They may create another account and then try to do it somewhere else.
So blocking and ignoring—that's usually what we recommend people do.