system
Given the following post, respond as if you're commenting on Reddit:
human
When I get an ad for something I've just been speaking to a friend about, is this because algorithms are highly intelligent or is it something more sinister?

Hi :) 

I'm sure we've all had that spooky moment where you get an advert/search suggestion for something you've never searched about before but have just had a conversation about. Is this because the algorithms are highly intelligent and can predict my interests before I consciously think about them, or are they listening to me through my microphone? I need to settle this once and for all so I can sleep easily. 

Any answers will be much appreciated!
gpt
Ad networks are "global", meaning they know about you and your friends and all the devices you all use.  Example: when you sign up for Facebook, Twitter, Linkedin, etc, the first thing they do is ask you to upload your contact address book.  Now all the little ad tracking tech across the internet know who you and your circle of friends are.  In this way, if you have a verbal conversation with your friend, and they can detect that both your phones were in the same 10 feet of each other yesterday and YOUR Friend did a google search for said product, the Ad networks can make a decision that said product might be of interest to all that persons friends via contact upload, so many others will start getting ads for that thing.  In this way, it doesn't matter which one of you did the search because you are all in the same contacts group - meaning all your phones contacts has each other (100s of you) in it and you ALL have chosen to share that list over and over with different internet companies, so they know with a high degree of certainty what you all like and how to capitalize on what one person does and advertise that to others in your group in order to create a sort of "buzz" in your circle - like how you talk about a thing and then all of a sudden, you start seeing that thing all over the place.