Actually, it might very well happen that these Wifi networks all have the same SSID, which would likely make most devices automatically connect to them.
Even if they don't, they only ever need one connection to link your device's MAC to your username, and then detect it without ever connecting.
Re:Get Facebook WiFi for your business
by MartinCron on Tuesday January 07, 2014 @04:48PM
(#7020217)
Yeah, I thought of that the moment I posted.
Nobody is forcing you to check in at your gynecologist's office, which is something you can already do, if you're into that kind of oversharing