I disagree that the "Do-Not-Track header is a perfect solution to this", because it implies that the default (i.e. the header being absent) should allow sites to track you. I (and apparently EU legislators) think opting in to privacy is wrong. You should have privacy by default. If anything, there should be a "Creepily-Track-My-Activity-Over-The-Entire-Internet" header, that, when present, allows tracking.
There also used to be another standard called "P3P" that tried to integrate privacy into browser UIs with a more or less standardized interface and that, too, failed. Among other reasons because companies wanting to track people subverted it.
There also used to be another standard called "P3P" that tried to integrate privacy into browser UIs with a more or less standardized interface and that, too, failed. Among other reasons because companies wanting to track people subverted it.