The right to be left alone. Garbo craved it. Brandeis defended it. And the Fourth and Fifth amendments to the US Constitution uphold it. In Olmstead v. United States (1928), Mr. Justice Brandeis declared, "The right to be left alone is the most comprehensive of rights, and the right most valued by a free people."

But protecting that right is becoming more difficult. Marketers expose the people of the United States to some 12 billion display ads, three million radio ads, and more than 300,000 television commercials daily. The unsolicited electronic junk mail known as "spam" now makes up about 10 percent of all e-mail around the world. An average US consumer is buffeted by roughly a million marketing messages a year across all communications media, or about 2,750 a day. Even worse, companies use private information ferreted out from daily commercial transactions, financial arrangements, and survey responses not only to inundate consumers with this kind of marketing rubbish but also to deny them credit and insurance.

Indeed, the very lingo marketers use to describe their methods of finding and influencing customers—military metaphors like "target," "campaign," "deploy," "blitz," and "capture"—betray an increasingly confrontational mentality about how companies should treat...