Since the Charlie Hebdo murders 10 months ago, France has been on high alert against possible terror. Authorities knew that attacks on Paris were being planned, but could not prevent the killing of 129 people, the wounding of many more — and the growing uncertainty about what to expect in the future. Was there too little information about thousands of possible suspects, or were investigators overwhelmed by too much data? Should the US give the NSA new power to intercept private messages, or is that too high a price for a strategy that hasn't been proven to work? And what about YouTube, Facebook and other public media used for terrorist propaganda and recruitment? Is it time to crack down on Silicon Valley?