It's all about finding people and stickiness
From Malcom Gladwell's "The Tipping Point":
The Law of the Few says that there are a few exceptional people out there who are capable of starting epidemics. All you have to do is find them. The lesson of stickiness is the same. There is a simple way to package information that, under the right circumstances, can make it irresistible. All you have to do is find it.