[nmilo]

I've always read comments like this and just assume it's confirmation bias on two levels:

1. Out of the 1000s of ads you see every day, at least one of them might coincidentally relate to something you talked about. You don't notice all the ads that are wildly irrelevant.

2. Even if you personally didn't have a hyper-relevant ad experience, out of the 1000s of HN readers that might comment a reply, one of them surely did. You just might be the one lucky guy that got your hyper-relevant ad of the day.

[plagiarist]

IDK, I think it is plausible they might be joining by IP or deeper connections. I've seen some ads that aren't relevant to me but are for something my partner was looking at on a different device.

[drdaeman]

It's probably simpler than this - advertiser just runs a campaign with some broad criteria (like income estimate based on IP-geolocated ZIP code) that both people in the same household fit. No surprise the same ad that one person had seen (and remembered) will be eventually shown to the other.

[adamrezich]

years ago I moved back to my hometown in South Dakota after a few years in Washington. my mom asked me to pick up some groceries for her and gave me her credit card to pay for it. I bought the groceries and, additionally, the first Red Bull I'd had in at least a year, using her credit card. within an hour, I got a notification from that one Google app thing where you answer survey questions for Play Store credit (not sure if it still exists), asking what my opinion of Red Bull was.

to reiterate:

- I had just moved halfway across the country

- this was the first Red Bull I had purchased in at least a year

- I made the purchase using a credit card other than my own, which was in no way connected to any bank account that was connected to me

- there should have been nothing connecting me to my purchase

I uninstalled the app immediately after that. sure, maybe it was some strange coincidence, but there's been far too many strange coincidences like that to make me anywhere near comfortable with this shit.

another time, years ago, I was talking to someone about how I needed to get a new pair of cheap earbuds, and within a couple hours an Amazon ad for this specific thing appeared in my Twitter timeline.

additionally, I just got married a couple weeks ago, and my wife and I immediately started seeing ads for sexual stamina tablets in our social media feeds—thanks, evil advertising apparatus, I thought I was doing okay :/

[njharman]

There's household device linking. One reason, streaming services/smart tvs want you to link phone/stream from phone. And all those services that want your phone number to verify/provide "2 factor". Yeah, they're totally not doing that to link phone and sell for future targeted ads.

There's many other ways devices can be linked, addresses of bills for instance.

[Ekaros]

Co-worker posted to company chat that they had failed to make some payments and then had got phising mail for their bank. Wondering was this linked. Later someone pointed out that phising had come before those failures. So was completely unrelated in reality.

All the conspiracy theories out of the window...