A lot of people said Facebook ads suggest them products or services debated on phone calls.
If you have Echo or Kindle Fire TV, guess it can be easily reproduced when Amazon really listening and analyze your voice.
Receiving baby items ads while no one knows your wife is pregnant ? Well maybe she googled a brand of baby strollers and fb used its graph + the fact that you're at the same location everyday after work to determine you're her husband.
Receiving ads for a small music band you only heard at that open mic night you randomly joined 3 days ago ? There probably was an event on fb with the list of bands that played that night + logged in the bar wifi.
With the number of people in the "hacker" community who want to prove fb and google are bad we'd already have real technical proof of it happening. Either they send the data back to a server and process it there, or process it on the device directly, both of which should be fairly easy to detect.
Agree. Here's something like video proof from BBC: https://www.bbc.com/news/technology-35639549
The behavior doesn't even need to "make sense" - it could be that people who log on at these times, live here, travel by train, like dog photos and belong to certain groups are highly to be interested in a particular product. It doesn't matter, the system will learn these relations anyway. It might seem spooky and eavesdropping-y from a naive user's perspective, but the simple fact is that when you have that much data you don't even need to eavesdrop.