[flashman]

"Facebook will also now know you visited a store based on a new feature that matches GPS, beacons, WiFi, radio signals, and cell towers with brick-and-mortar coordinates." [1] Basically harvesting data from your phone's sensors, where their app is installed.

And: "A new Facebook API, called the Offline Conversions API, works with a number of in-store sales systems from companies like Square and IBM to match their customer data with Facebook’s advertising data." [2]

(More science-fictiony: they could broadcast a local audio signal that fingerprints a particular location. Hmm, startup idea.)

[1] https://techcrunch.com/2016/06/14/facebook-knows/

[JoshMnem]

That's terrible. I hope that removing all of Facebook's software from a phone and using cash prevents that. I hope you're joking about the audio signal.

[jmgrosen]

Not quite used for in-store advertising, but Google's "Nearby Messages API" does use "near-ultrasound" audio signals to communicate with other devices: https://developers.google.com/nearby/messages/overview. I don't know if it would work at a larger scale, though (maybe you couldn't allow dogs in your store!).

[JoshMnem]

Also used for other purposes. Consumers would never consent to it if they understood it.

https://www.wired.com/2016/11/block-ultrasonic-signals-didnt...

https://arstechnica.com/tech-policy/2015/11/beware-of-ads-th...

https://www.theatlantic.com/technology/archive/2015/11/your-...

[nissimk]

So that's why it destroys my battery.