"One of the things I'd like to do is to show people how to start "positive" epidemics of their own. The virtue of an epidemic, after all, is that just a little input is enough to get it started, and it can spread very, very quickly. That makes it something of obvious and enormous interest to everyone from educators trying to reach students, to businesses trying to spread the word about their product, or for that matter to anyone who's trying to create a change with limited resources." This is from The Tipping Point.
I think I will have to read this book. More about Gladwell here.