In February 2009, Alex Zablocki and I used Facebook to organize the New York City Tea Party, one of the first Tea Party protests in the country. Several thousand people joined our Facebook group, which we used to organize our first Tea Party protest. Hundreds of people showed up, we passed around a bullhorn, and we officially became “Tea Party organizers.” Without Facebook our rally would have most likely attracted about 20 people. Facebook was powerful and we knew it. Our next Tea Party rally, also organized through Facebook, brought 12,000 people to City Hall in Lower Manhattan. A social...