I used to work in digital advertising company that had their on DPI technology and had deals with ISPs to tap into their network and some publishers. We profiled each user, by default it was opted in (: after some pressure it was by default opt-out but whoever was opted in and didn't know that remained opted-in. China was just meh, everybody opt-in we don't care about your privacy....

Truly ingenious technology but everything else was shit, truly bad moment in my career that fortunately lead to a better place for me...

(Also this was pre-https everything so it was super-easy to sniff the traffic)