“Some have argued that with new technology there is a diminished expectation of privacy,” said Marc Rotenberg, executive director of the Electronic Privacy Information Center, a privacy rights group in Washington. “But the opposite may also be true. New techniques may require us to expand our understanding of privacy and to address the impact that data collection has on groups of individuals and not simply a single person.”

Mr. Brown, for one, isn’t concerned about losing his privacy. The M.I.T researchers have convinced him that they have gone to great lengths to protect any information generated by the experiment that would reveal his identity.

Besides, he says, “the way I see it, we all have Facebook pages, we all have e-mail and Web sites and blogs.”

“This is a drop in the bucket in terms of privacy,” he adds.

GOOGLE and its vast farm of more than a million search engine servers spread around the globe remain the best example of the power and wealth-building potential of collective intelligence. Google’s fabled PageRank algorithm, which was originally responsible for the quality of Google’s search results, drew its precision from the inherent wisdom in the billions of individual Web links that people create.

The company introduced a speech-recognition service in early November, initially for the Apple iPhone, that gains its accuracy in large part from a statistical model built from several trillion search terms that its users have entered in the last decade. In the future, Google will take advantage of spoken queries to predict even more accurately the questions its users will ask.

And, a few weeks ago, Google deployed an early-warning service for spotting flu trends, based on search queries for flu-related symptoms.

The success of Google, along with the rapid spread of the wireless Internet and sensors  like location trackers in cellphones and GPS units in cars  has touched off a race to cash in on collective intelligence technologies.