Social network marketing is an advertising method that makes use of social network service. This ranges from simply advertising directly on social network sites such as Facebook, MySpace, or Cyworld, viral marketing that spreads throughout the web, email, and word of mouth or providing niche social networking sites focused around the item being advertised. New research by Harvard Business School Professor Sunil Gupta suggests that viral may be the way to go in these connected worlds. "By understanding the social network of users, firms can better understand and influence consumers' behavior," says Sunil Gupta.