Public interest groups, advertisers at odds over feasibility of 'Do Not Track' list

"'Do Not Call' has been a unique success — creating the digital blueprint for what needs to now be done online," said Jeff Chester, a privacy advocate and president of Center for Digital Democracy. "Tens of millions of U.S. consumers have been easily empowered to stop unsolicited commercial phone calls coming to their homes."

He said its "just common sense" to extend the same protections into the digital era by creating a "Do Not Track" system.

Still, amid the mounting enthusiasm for a simple-to-use system, privacy advocates and online advertisers are split on the technological feasibility of the plan. 

Consumer advocates say the obstacles to the system are policy-related and not technological. Lee Tien, a senior staff attorney at the Electronic Frontier Foundation, which advocates for stronger online privacy regulations, said there are simple technological solutions to the problem. A browser that tells a website that a consumer does not want to be tracked would be one simple fix, according to Tien.

The difficulty, he said, is making sure a regulatory framework is in place to force Web advertisers to comply.

"The question is really about policy and not technology," he said. "It's inaccurate when people say the technology isn't there."

It might be hard to tell if advertisers are complying, he said, but if ads that seem a little too targeted appear on the side of the screen, that will be a dead giveaway.

Some digital advertisers insist the technological barriers are higher than Tien described. While "Do Not Call" has been a success, online technology evolves faster than phone technology, making it more difficult for the system to keep up with the latest tracking methods, experts say.

Harlan Yu, a researcher at the Center for Information Technology Policy at Princeton University, said there are limits to what browsers can do to make "Do Not Track" feasible. Tracking sites can run complicated scripts to disable a browser's ability to hide a user's identity.

If the browser can't do it, problems arise, Yu said. Even a solution where the browser communicates with the tracking site, which is then bound by regulations to comply, could be problematic.

One problem is websites could work to destroy the system, offering only limited content to browsers who opt out of tracking.

"One issue is bifurcation: Nothing would prevent sites from offering limited content or features to users who choose to opt-out of tracking," Yu said.

The result could be a "divided Web" where a user who turns on the "no track" option on their browser "would essentially turn off many of the useful features on the Web," he said.

A remedy could be "tracking neutrality rules," Yu said, forcing sites to offer the same content to users who opt not to be tracked.

"Suffice it to say that crafting a narrow-yet-effective neutrality provision would be highly contentious," he said.