I love this blurb from Felix Salmon of Reuters:
To build a mass movement quickly, it helps to have an over-simplified, emotive narrative with a single demand. It also helps to tell people that by doing easy tasks -- sharing a link on Facebook, buying a bracelet -- they can make a material difference (e.g., save lives). Central to the formula is that the agency of "local actors" gets downplayed to hype up the importance of action by outsiders.