IE10 has a negligible share: Neither Net Applications nor StatCounter have begun tracking it.
It's unclear how the W3C will, or even if it will, resolve its differences on IE10 to, for instance, either demand that websites honor its DNT signal or allow them to ignore it.
Harris and Brookman of the CDT wondered where it would end, too. But one possibility would kick off what they called a "privacy arms race" pitted with tit-for-tat responses by advertisers and Microsoft to block, unblock and re-block DNT.
"The result would be turning the online ecosystem into an ever-escalating war between privacy interests and advertisers, precisely the war that a negotiated Do Not Track setting was designed to avoid," said Harris and Brookman.
Others have noticed a change in advertisers' tone in the most recent DNT discussions. Last week, Federal Trade Commission chairman Jon Leibowitz told the Wall Street Journal that the industry "appears to be backing off from its commitments" made last February.
The FTC backs Do Not Track, but Leibowitz has not expressly thrown his weight behind Microsoft and IE10.
Microsoft on Wednesday declined to address the ANA's allegations, instead repeating a previous statement that said, "Our approach to DNT in Internet Explorer 10 is part of our commitment to privacy by design and putting people first."
In an op-ed piece in Adweek last month, however, Rik van der Kooi, Microsoft's top ad executive, said critics were losing perspective. "Instead of debating whether DNT is 'on' or 'off,' we should redouble our efforts as an industry and educate consumers about how advertising pays for the free Web experience we all now enjoy," van der Kooi wrote.
It may be difficult to get the two sides -- the ad industry and privacy-first advocates -- to agree when words like "outrage," "bizarre" and "unacceptable" are bandied by the parties.
The ANA, which did not reply to a Computerworld request to make someone available for an interview, asked Microsoft for a face-to-face meeting between executives. "We respectfully suggest an immediate dialogue with key Microsoft executives prior to the anticipated release of Internet Explorer 10," the trade group said in its letter.
Harris and Brookman had hope for a resolution. "At the end of the day, privacy advocates will have to settle for something less than they would like in an ideal world [and] advertisers must honor their commitment to comply with users' Do Not Track instructions," they said.
The debate isn't limited to the U.S., as European regulators have also weighed in on DNT, and expressed support for Microsoft's position on IE10.
"[The advertising industry] now stands in open defiance of policymakers on both sides of the Atlantic and, more importantly, the tens of millions of users who have enabled Do Not Track in their browser," said Mayer. "[But] the primary effect of their efforts has been to call more attention to Do Not Track."
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