Courts have refused to treat violent content as they would sexual material, which government can restrict under longstanding obscenity doctrines.

WSJ: High Court Strikes Down California Videogame Law

Social media such as Facebook are sometimes blocked, and some games in Vietnam have been taken down, mostly because of violent content.

FORBES: Companies, People, Ideas

The Pan European Game Information system (Pegi) gives games an age rating as well as additional information such as violent content and bad language.

BBC: Person buys Grand Theft Auto IV

That counts as exposure to violent content, and Dr. O'Keeffe says it can be especially scary to big kids, who understand that it's real.

CNN: Is media violence damaging to kids?

Clinical research about whether violent content can desensitize the brain to violence, making a person more likely to commit some atrocity, is varied and uncertain.

FORBES: A Chilling Link Explored Between Gunmakers And Video Game Companies

The FCC itself has recognized that its inability to oversee violent content is a problem and in a 2007 report to Congress called for changing the rules.

WSJ: Campbell Brown: The President Gives Hollywood a Pass on Violence

Songs tagged for violent content and live shows that ended in food fights... well, that may or may not be "just plain fun, " but those can be checked off the list, too.

NPR: Be Your Own Pet: Teenage Abandon

The music industry already places parental advisory "explicit content" labels on records with sexually graphic or violent lyrics, but does not give details of the offensive material.

BBC: Rap boss crashes Senate hearing

The lawyers from the band's major-label distributor found the content in "Becky" and two other songs too violent and told Be Your Own Pet to either change the lyrics or take them off the album.

NPR: Be Your Own Pet: Teenage Abandon