Volvo is using its Twitter fans to test creative ideas through its agency Arnold Worldwide. One spot, which features an ostentatiously dressed Chihuahua, displeased some dog owners, for example. "It's creating good conversations; people enjoy being part of [the creative process]. Feedback helps us find the right balance," says Tassos Panas, North American chief marketing officer. The effort has doubled traffic as fans seek to weigh in with opinions, Panas noted.