A new study released today has shown that consumers are less anonymous than they think they are when surfing the web, prompting calls for "do not track" policies.

According to the Computer Security Laboratory at Stanford University, more than half of the 185 high-traffic sites examined in a study shared a consumer's username or user ID with another site. Among the top recipients of username and user ID information were Facebook, Google, comScore and Quantcast.

Jon Leibowitz, Federal Trade Commission Chairman, said the study would aid in the agency's efforts to protect the online privacy of consumers while keeping at bay what he referred to as the "cyberazzi." He likened the online practice of behavioral advertising and data collection to the paparazzi known for tracking the moves of celebrities.

"A host of invisible cyberazzi, cookies and other data catchers follow us as we browse, reporting our every stop and action to marketing companies that in turn collect an astonishingly complete profile of our online behavior," Leibowitz said at a privacy forum at the National Press Club on Tuesday.

He added that he envisions a system that would be easy for consumers to use "and one that all companies employing cyberazzi have to respect." The FTC backed the creation of a "do not track" option for the Internet in a preliminary staff report issued late last year. The option would limit the ability of advertisers to collect consumer data.

Leibowitz singled out Microsoft Corp., Mozilla and Apple Inc. for integrating "do not track" features into their browsers and added that he hoped Google would as well. He said that while the FTC has no intention of ending behavioral advertising, they advocate giving consumers streamlined and effective choices about the collection and use of their data.

"I believe we can keep cyberazzi lenses focused on willing subjects and at the same time ensure the right of all citizens to choose the public faces we present to the world," said Leibowitz. While legislation has been introduced in Congress to allow consumers to opt not to be tracked, it has gained little traction so far.

According to Jonathan Mayer, author of the study, information leakage is a pervasive issue. He added that 61 percent of websites he interacted with leaked either a user ID or username.

"Many times, developers are not thinking about privacy issues, and it's a fact of life that information is going to leak to third parties," said Mayer, a graduate student at Stanford. "I think we have to recognize that's just the way the Web works."

The study showed that by signing up on the NBC website, a user's email address was shared with seven other companies. While viewing a local ad on the Home Depot website, a user's name and email address were sent to 13 companies.

"If you can have 'do not track,' you will instill in consumers the kind of sense of control that builds faith in the Internet," said John Simpson, privacy project director for the nonprofit Consumer Watchdog.