The coincidences are generally amplified by the fact that apps generally do send location data, when you visit friends you generally talk about stuff you've bee

The coincidences are generally amplified by the fact that apps generally do send location data, when you visit friends you generally talk about stuff you've been looking at lately, so it certainly plausible that linking profiles based on proximity and similarity of interests would mean that there's a much higher chance that advertising interests spread from one user to another, merely by geography.