Mozilla, in fact, had staked out its position earlier.

"At its foundation, DNT is intended to express an individual's choice, or preference, to not be tracked," said Alex Fowler, who leads Mozilla's privacy and policy work, in a written the same day Microsoft said IE10 would have the signal on by default. "It's important that the signal represents a choice made by the person behind the keyboard and not the software maker, because ultimately it's not the browser being tracked, it's the user."

Firefox, Fowler continued, supports DNT, but leaves it in the "off" position which lets -- or makes, depending on the viewpoint -- the user choose. "For DNT to be effective, it must actually represent the user's voice," Fowler said.

Either Microsoft or the W3C group will have to blink. And it doesn't sound like the W3C will be the one to back down.

"This is as far as we're willing to go," said Jonathan Mayer, also a researcher with the Stanford CIS. He was referring to the group he called "privacy-leaning parties" who, he said, have compromised as much as they're going to.