Word of mouth, then, is a prime tool for making a good impression—as potent as that new car or Prada handbag. Think of it as a kind of currency. Social currency… So to get people talking, companies and organizations need to mint social currency… There are three ways to do that: (1) find inner remarkability; (2) leverage game mechanics; and (3) make people feel like insiders.
– Jonah Berger, Contagious: Why Things Catch On