There have been several articles written about Firefox's Do Not Track feature that are basically asserting it's a failure because "Less than 1% of Firefox Users Use 'Do Not Track'".
I have one very simple response to that:
What do you think that percentage would become if Firefox alerted a person when she was being tracked with something like, "The site, http://foopy.com, is tracking you. Would you like to tell sites to stop tracking you?"
Tracking is invisible to most people so blocking tracking isn't high on a person's list of decisions when online. Make it visible and I'll bet those numbers change in a hurry.