[netsharc]

Thought experiment: your phone could know you liked a particular tourist spot because you spent a lot of time there, and later on when you upload pictures from your DSLR to Google Photos, the system will notice that there are a lot of photos that are timestamped within the time range when you were at that tourist spot.

And data mining can tell that people who like that tourist spot A in country X also liked tourist spot B in city G in country Y a lot, so, tourism board of city G/country Y, here's a good target for your ad.

And not just tourist stuff. Data mining might even tell they like a particular brand of, I don't know, yoghurt, so let's sell some of that yoghurt!