From the official YouTube blog:

Like you, we’re continually surprised, moved, and entertained by the videos people post on YouTube. And, like you, we’re occasionally dismayed when people use YouTube for less positive purposes. That’s why we count on you to know our Community Guidelines and flag videos you believe don’t belong on the site.

We’ve recently made a change to our flagging menu we think you should know about: We replaced the category “minors fighting” with “youth violence.” You can find it in the pull-down menu under “Violent or Repulsive Content,” and we’ll still follow our usual process of reviewing all flagged videos quickly and removing those that violate our Guidelines.

The reason for this change in language is simple: We want to make it easier for you to help us take down the increasing number of videos showing children involved in violence of some sort, including threats and actual altercations. The “minors fighting” flag simply wasn’t being used enough, yet the number of these kinds of videos has been increasing. Now you can more easily flag violent videos that include underage people, and we’ll take it from there.

Think of the Guidelines and the flagging pull-down menu as part of our ongoing conversation with you. We give you a structure that makes it easier for you to talk to us, and you become the eyes and ears of the site. Of course, the best conversations are never static, and the same is true about this one. We’re always reviewing our Guidelines and the flagging categories to make sure they reflect what you see on the site.

The new flag is part of a larger, continuous effort here at YouTube to keep the community safe for all of our members. But we can’t do it alone.