Social networking is the most significant business development of 2010, topping the resurgence of the U.S. automobile industry. During the year, social networking morphed from a personal communications tool for young people into a new vehicle that business leaders are using to transform communications with their employees and customers, as it shifts from one-way transmission of information to two-way interaction. That's one reason Time magazine just named Facebook founder Mark Zuckerberg Person of the Year.