Microsoft's plans to enable Do Not Track flags in Internet Explorer 10 by default have taken a setback this week as the latest draft of the DNT specification explicitly states that the user must be given the choice. You might recall that the original W3C proposal for Do Not Track was actually titled "Tracking Preference Expression," and this latest revision to its wording is reflecting the importance placed on those words — the sending of Do Not Track signals to websites from your browser must only happen as a direct expression of your will. Thus, any browser that defaults to either enabling or disabling DNT without asking the user to choose which she prefers is in breach of the spec as it currently stands.
Microsoft is still free to continue with its plans, however it would not be able to say it adheres to the proper Do Not Track specification if it does, and many websites and advertisers may opt to ignore its flags as a result. Their argument would be that it's up to users to signal they do not want to have their web browsing tracked — which, ironically, Microsoft's stated plans for IE 10 do not allow.