Ofcourse I know that my smartphone broadcasts its mac/stored-essids every few seconds, thats why I have wifi disabled most of the time. Most people don't realize that, most people also don't realize the tracking capabilities of cookies. Laws in EU have begun to make it illegal to store cookies without the users consent, because even though its technically possible to block cookies, most people have no idea about that. So I can only hope that it will become one day illegal to violate peoples privacy like that!
Also, people log in with Facebook to basically anything.
"it's free" and "get cool rebates" create such an incredible variant of SEP field[0].
https://meraki.cisco.com/blog/2013/12/get-a-visual-on-your-b...
So people are probably already being tracked... and no one has noticed.