According to a New York Times article by Natasha Singer (13 October 2012), 9 members of the US House of Representatives questioned the Federal Trade Commission's "involvement with an international group called the World Wide Web Consortium, or W3C, which is trying to work out global standards for the don’t-track-me features." What apparently has them distressed is that "do not track" may become the default in, for example, Microsoft's new version of its Internet Explorer browser.
Defaults are important, as Richard Thaler and Cass Sunstein explain in their Nudge.blog. People tend to accept defaults rather than change them, and this is true for a wide variety of topics including pension plans, health care, and privacy. Those who control the choice of the default arguably determine what a majority will decide. This is not surprising, since we accept cultural defaults all the time in matters as basic as food and clothes.
After years of working on operating systems and on network applications, I am perhaps less concerned about privacy than many of my colleagues for quite contradictory reasons: first, because I realize that anyone with the right technical skills can break ordinary privacy protections in the Internet, and second, because I realize that it is a lot of work and mostly not worth the trouble. Nonetheless some regard for privacy seems basic to how free and democratic societies operate in the HTTP environment. Microsoft seems to have consumer interests more at heart than the nine US congressmen.