The Tipping Point, Malcolm Gladwell
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Gladwell outlines the steps, factors, whatever that need to occur to make an small-time idea a big-time reality. He shows how different types of people play key roles. For instance, 'Mavens' are they type of people to find good ideas, and 'Connectors' are the ones to hook everyone up with the idea. It's a really fascinating book, and from what I've heard Malcolm Gladwell is a reliable source.
I'd encourage anyone who is interested in how trends in thinking come about, or who seek to influence trends in thinking (say, get people thinking they should be changing the world) to read this book.