Facebook CEO Mark Zuckerberg once said it was a "pretty crazy idea" that the social network he created might have influenced the 2016 presidential election. The idea suddenly doesn't seem that crazy, considering the scope of Russian activity online around the election. Facebook, Google and Twitter representatives were called before Congress to explain how their technology may have been misused. What answers did the tech giants provide? And must Congress act to protect Americans from liking, tweeting and searching themselves into uncharted territory?