DNT was DOA.
What site in their right mind would actually honor - and I mean fully, including through any third party content (and yes by that I mean ads) or 'accidental' methods via supercookies / sharing of information at the backend of several sites within one's control - something that's merely a 'request' by a user (regardless of whether they were semi-automatically opting into making that request) and has no legal stick behind it?
If anything, Microsoft making it the default in Windows' installation express settings just exposed exactly this issue when sites started saying they would ignore the setting "because Internet Explorer". That was always a completely transparent bullcrap excuse.
Just have a look at what countries with strong 'cookie' laws have going on. Are there some sites that do disable the tracking cookies while leaving cookies for functionality up? Sure, of course they exist. And for every single one of them, there's dozens that will throw a banner in your face suggesting that you have a choice: allow the tracking cookies, or piss off.
Some might say "so piss off and go to another site" - except there often is no such other site, and most people given the choice between being able to consume and not being able to consume at the expense of intangible tracking will happily be tracked so the sites never feel it in their bottom line either.
This is the sort of thing that I would expect to happen with DNT as well: A banner with something like "You currently have DNT enabled - to access the rest of this article, please disable DNT or click here to allow our servers to store information about your visit this once.", which eventually gets old and users disable DNT.
And yes, that sort of thing is facilitated in the DNT spec: http://www.w3.org/TR/tracking-...
DNT was never going to get anywhere particularly useful for end-users while adding a layer of headache on the server side. Browsers' default behavior and browser extensions have done far more to inform users of the issues of ads and tracking and how to mitigate those issues.