Yahoo alluded to that on its blog, saying, "In our view, [IE10's on-by-default] degrades the experience for the majority of users and makes it hard to deliver on our value proposition to them."
"Value proposition" clearly refers to the trade-offs -- users must accept the targeted ads as the price for receiving free software, services and content -- that advertisers say make the Internet what it is. As far as advertisers are concerned, tracking is required to provide targeted ads.
A group composed of advertisers, browser makers, privacy advocates and others have not finalized a DNT standard, even after months of intensive work. The Worldwide Web Consortium (W3C) standards-setting group has, however, preliminarily ruled that browser makers cannot set the DNT signal for users, essentially letting each website decide whether it will acknowledge or ignore IE10's.
Advertisers recently turned up the rhetoric about DNT. Earlier this month, the Association of National Advertisers (ANA), an industry lobbying group, said Microsoft's decision would "harm consumers, hurt competition, and undermine American innovation," and called the on-by-default setting "unacceptable."
Privacy advocates countered, saying that the ANA's demands were "bizarre."
Yahoo's decision to ignore IE10's DNT signal is notable because the California company is allied with Microsoft in search. In 2010, the two firms signed a 10-year agreement whereby Yahoo's search results are fueled by Microsoft's Bing search engine.
One privacy advocate tied Yahoo's announcement to the Friday launch of Windows 8. "Hunch: Yahoo walked back its Do Not Track commitment today because of the Win8/IE10 launch," said Jonathan Mayer on Twitter.
Mayer is a graduate student in computer science and law at Stanford University, and one of two researchers at the school who created the HTTP header implementation that signals a user's DNT preference.
Microsoft debuted IE10 on Oct. 26 as part of Windows 8. A version of the browser for the much more popular Windows 7 will reach beta -- Microsoft calls that a "preview" -- in mid-November. IE10 on Windows 7 will also have the DNT option enabled by default.