I reactivated my Facebook account today to check a couple of 'must-see' posts that I couldn't see otherwise. It was beyond creepy to see it telling me that I 'might know' a person I met offline, and offline only. The only way they could have tracked us together was through our phones. Our phones were at the same location for couple of weeks. I think we took taxis using the same mobile app, separately. That is all. I've never used Facebook from my phone.