[nebulous_two]

There is an understanding between shopper and shop owner about what is happening on said property. The shopper normally does not expect that the shop owner would instantly know your entire biography + family lineage just by stepping onto the property.

[burntoutfire]

How can he get that from just a photo?

[heavyset_go]

From firms like this[1].

[1] https://www.vice.com/en/article/5dmkyq/heres-the-file-clearv...

[kevin_thibedeau]

You collect cell phone IMEIs and sell it to a data broker that aggregates multiple sources to pinpoint strong associations that lead back to a shopper's home. In return you get demographic data on your customers.