- User 1 shows an interest in <topic>.
- User 1 visits the same location, for the same period of time, as user 2.
- So I show an ad for <topic> to user 2.
And of course whoever you are performing your search with, like, oh, an ad company like Google, Meta, or Facebook? They just might use that search data for something.
I care about accuracy when it comes to privacy conversations. I don't want people wasting their time on theories that aren't true when they should be focusing on the real issues at stake.
On WiFi you control this risk can be mitigated (force DNS to your own server that uses ODoH or similar) but for most people ISPs are still sitting on data gold mines obtained from passively observing DNS.
In his case a realistic answer falls towards loose or sneaky permissions in regard of an app that have slipped through that have allowed a weird conversation to influence suggestions in internet activity later on.
However for more grounded subject matters, the more probable strange coincidences falls to queries and visits to the net being scraped by external API and content (fonts scripts etc) providers. I've no idea how much meaningful info would normally be shared between the site and third party providers that seemingly need to be contacted while a site loads.
Based on this assumption, it wouldn’t be necessary for any of your friends to search for the topic during an evening together.. it would simply be enough that one of the friends showed some interest in the topic prior to the hangout (searched for something, read a blog, stopped for too long on an instagram reel).
Then, during an evening together, your phones all share the same location (and possibly movement). That’s enough for advertisers to suspect there’s some relationship there. Enough of an association to attempt an ad placement (or instagram reel) for a particular obscure topic.
As such, if location or device id data were available to build a larger picture, for any sort of common topic I'd agree the advertising could easily be a result of data analysis of various subsets of phones in a given region, applying algorithms and feeding it back into search results.
However like I said, the stuff was apparently way way out there zany - he ensured me he would ever bother searching for it. So zany in fact no one would ever bother. For all I know he may have ruled out other people and have just been talking to his pet dog and various other tame native animals that hang around his verandah. I would tend to believe way way out there as after a small smoke around me he's dribbling worthless bs. There's no low bar on my part either - something like if polka dot dogs exist I could accept as something that might / could be searched the next day by anyone who was involved in such a out there conversation, and as a result skew search results.
Any how I'm settled on it's one of the many worthless apps on his phone that exists because a website is not desktop friendly - as they say if the service is free, you're the product ...