[jeannekamikaze]

The fact that you came again is likely a valuable piece of data. And now you are identifiable, so if this is scaled to several coffee shops (not that this particular one would, but as a general idea), you get some pretty decent location tracking right there without having to sell people expensive devices with elusive privacy controls. Probably somewhat of an overshoot (or maybe not?), but given that companies like Google sell you local ads based on where you are, I can see why this approach would be valuable.