[eli]

I think most ad/marketing companies are perfectly willing to stop tracking people who specifically request not to be tracked -- provided there aren't too many people making that request. Witness the opt-out cookies (http://www.aboutads.info/choices/) which are a kludgey hack, but have been supported by the industry for ages and, as far as I know, work as described.

The issue is whether or not that DNT box is checked by default. As we all know, most people don't change default settings.