assuming you mean respecting settings. historical data from before you blocked tracking wasnt explicitly deleted, but it was marked as ignored and rolled out o

assuming you mean respecting settings. historical data from before you blocked tracking wasnt explicitly deleted, but it was marked as ignored and rolled out of the system after a month or so(lots of caching). id guess with fb having orders of magnitude more data they do something similar. DNT is easy, thats a header on every call so just drop it on the floor. Unfortunately firefox was always threatening to make it on by default, and IE actually did i believe...and basically all the big ad providers threatened to ignore it if it went on by default. Management basically said we'd do whatever the industry does, but is currently respected. The problem with the opt out flow is how do you store that someone wants you not to store information about them without storing info about them. The standard way is drop a cookie that says dont track, but if you clear cookies youd have to opt out again... which is shitty UX and unexpected. also, since its cookies its opting out the browser, not the user or computer. As a consumer, it sucks because you have no way of knowing if the ad/tracking companies are respecting any of this. And while I'm positive we tried to respect it, and im not aware of any, bugs can happen. That code was part of the most heavily tested stuff since it hit critical paths. On most targeted ads(including but not limited to on facebook) theres a little adchoices(blue triangle) button. If you click on it you can see which company targeted you, some info on what type of targeting, and a link to optout.