By Om Malik Dennis Crowley has built his career at the intersection of emerging technologies and human behavior. Twenty years ago, as a 25-year-old inspired by Harry Potter's Marauder's Map, he created Dodgeball—turning text messaging into a way for friends to find each other in the city. When the iPhone emerged, he launched Foursquare, riding the convergence of GPS, apps, and our growing comfort with social networks to transform how we interact with places around us. Google bought Dodgeball in ...