Social networking sites such as are some of the most trafficked on the Web—MySpace had 46 million unique users in June and features nearly 100 million personal profiles posted by users, many of whom are in their teens and twenties. What's more, the average MySpace user clocks two hours per visit on the site.

But MySpace and its rivals have also come under fire from law enforcement officials, policymakers, and parents, who worry that they are a haven for child predators.

Given that backlash, is MySpace a safe bet for advertisers? Apparently so. To market their summer movies, a number of Hollywood studios struck advertising deals with News Corp, MySpace's owner, including several who crafted profile pages featuring movie characters.

HBS Working Knowledge interviews John Deighton, the Harold M. Brierley Professor of Business Administration at Harvard Business School and an expert on interactive advertising, for a quick overview of the MySpace phenomenon.

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