Epidemics are, at their root, about this very process of transformation. When we are trying to make an idea or attitude or product tip, we’re trying to change our audience in some small yet critical respect: we’re trying to infect them, sweep them up in our epidemic, and convert them from hostility to acceptance. That can be done through the influence of special kinds of people, people of extraordinary personal connection. That’s the Law of the Few. It can be done by changing the content of communication, by making a message so memorable that it sticks in someone’s mind and compels them to action. That is the Stickiness Factor. I think that both of those laws make intuitive sense. But we need to remember that small changes in context can be just as important in tipping epidemics, even though that fact appears to violate some of our most deeply held assumptions about human nature.

— The Tipping Point: How Little Things Can Make a Big Difference by Malcolm Gladwell