• by Wendy Davis , Staff Writer @wendyndavis, February 23, 2012

This week, after years of debate, the ad industry has agreed to support a universal, easy-to-use, do-not-track tool that will enable consumers to opt out of all behavioral targeting.

The do-not-track terminology dates to the fall of 2007, when a coalition of privacy advocates asked the Federal Trade Commission to endorse the idea that consumers should be able to opt out of all behavioral targeting through a single mechanism. The FTC did so in 2010, but ad companies were slow to embrace the idea. Instead, industry groups said that consumers who wanted to avoid online behavioral advertising could opt out from targeting on sites run by self-regulatory groups, or at individual companies' sites.

Privacy advocates responded that those cookie-based opt-outs were problematic. One issue was that cookies aren't stable because they get deleted -- either by users or by the sites. Another is that opt-out links sometimes were broken.

On Wednesday, Stu Ingis, counsel to the self-regulatory group Digital Advertising Alliance, told reporters that the organization will support the do-not-track header. "The DAA will immediately begin work to add browser-based header signals to the set of tools by which consumers can express their preferences," Ingis said.

This statement means that Google, Yahoo, AOL and other companies that have publicly committed to follow the DAA's principles  must honor do-not-track headers or risk FTC charges for engaging in deceptive practices.

Mozilla has already developed a do-not-track header for Firefox users, but only a few ad networks had publicly agreed to honor it until this week. Users nonetheless have been adopting the header. Seven percent of desktop users and 18% of mobile users activate the header, Mozilla reports.

Privacy advocates like the Center for Democracy & Technology cheered the news that the industry will support the do-not-track header, but also acknowledged that much is still unresolved.

"For five years CDT has pushed for the development of a reliable 'Do Not Track' mechanism; today's Digital Advertising Alliance announcement is an important step toward making 'Do Not Track' a reality for consumers," CDT's director of consumer privacy, Justin Brookman, said in a statement. "The industry deserves credit for this commitment, though the details of exactly what 'Do Not Track' means still need to be worked out."

One of those details centers on whether companies should be able to collect any data about consumers who have activated a do-not-track setting. 

The Digital Advertising Alliance prohibits ad networks from collecting  information about users for purposes of online behavioral advertising when they have opted out. The DAA also prohibits members from collecting any information about Web users in order to determine their eligibility for employment, credit, health care or insurance.

But self-regulatory principles allow companies to track consumers for purposes like analytics, frequency capping and site optimization, even when consumers have opted out of online behavioral targeting.

The World Wide Web Consortium, which is creating standards for do-not-track, says it is still in the process of "building consensus around global Web technology that will allow users to express a preference regarding being tracked online, and what is necessary to comply with the user's preference."