The fact that I still get snail mail spam catalogs in my mailbox each day, with no mandated option to opt-out, I see no way that marketers will respect DNT. The gov't seems to believe that the economy relies on its ability to market to consumers, even if they don't want to be targeted.
Reminds me of Richard Feyman taking LSD. He said he had an incredible breakthrough and a moment of pure clarity on a problem he had been working on mid-trip, only to come down and realize his breakthrough was really jibberish and not insightful at all.