The Influentials: One American in Ten Tells the Other Nine How to Vote, Where to Eat, and What to Buy by Jon Berry and Ed Keller
If you read the Tipping Point, you can skip this book. The book hashes a lot of data about which consumers influence others, but the entire 343 page book could be better condensed to a 5-page memo.
Please love this book. But my summation: Skip it.