Summary: Mass shootings in Paris, Colorado Springs and San Bernardino have generated more pressure than ever on YouTube, Facebook and Twitter. They're being asked to monitor messages worldwide, alert federal officials and take threats and hate-speech off line ? without becoming agents of government or ideological censors. At the local level, the LAPD and county sheriffs rely on community partnerships to find out when ideas might turn into violent action ? at the risk of religious profiling that's illegal and counter-productive. We look at challenges that can't be avoided.
