Two ways I'm aware of. If your time at the coffee shop is regular (arrive at 3:15 because that's when your break is from work) they can place you with other reg

Two ways I'm aware of. If your time at the coffee shop is regular (arrive at 3:15 because that's when your break is from work) they can place you with other regulars (you go there with your wife every day after work, you get dark roast and she gets a tea). Second if you're a black hole of privacy features and everyone else around you is not... well you get identified that way. Like herd immunity there is a risk if your behavior makes you an outlier. Imagine for a moment though that they can't serve you ads directly. I wonder if anyone has done research into saturating adds in a coffee shop for all the patrons? Everyone sees the same add for the Dallas Cowboys and triggers a conversation about football. Now you didn't see the add but everyone around you is talking about football.