It's one of the hottest industries in America. Easier to order at home than a pizza, bigger than rock music, it's arguably the most profitable enterprise in cyberspace. AT&T has been in the business. Yahoo! has profited from it. Westin and Marriott have made more money selling it than selling snacks and drinks in their mini-bars. And with estimates as high as $10 billion a year, it boasts the kind of earnings that most American businesses would envy. It's pornography.

• Documentary