Here's how it worked ~12 years ago: At some point you almost certainly have used the same home internet connection. A cookie associated with some account(s) of hers gets associated with that IP. Same for some account(s) of yours. Find IPs that over small time frames only have a handful of distinct users to filter out coffeeshops and such. Bam, likely family or roommate connection. Some sticky "supercookie" stuff or similar gets set so this can be both resurrected even when cookies expire (through like Etag cache headers or whatever) and then there's a lot of behind-the-scenes ad network offline-cookie-syncing.
One of the companies in that web partners offers ads on FB, another runs ads on Google, she searches and click something on your wife's phone (at this point regardless of network), it gets tied to you too.
It could be more innocuous but tracking same-household, cross-device for retargeting... all that is really old hat at this point.
I intentionally moved my career pretty far from ad-tech in the past decade, but from what I've heard in adjacent convos and such is that the newer developments include some of the newer platforms like smart TVs into all that old cross-device fun, too. Both as data source and ad display destination. A lot of TVs phone home about what you watch, even - like https://clinch.co/clinch-partners-with-samsung-ads/ There's a million ad-tech companies out there, they aren't all just writing real-time-bidding algorithms for traditional display ads.
But the serendipity it can create is truly wild.
Tracking is easy, intelligent personalization is hard. But tracking alone takes a lot of constant investment with tech development and arms race and all.
But every time I read something like this, I am puzzled how they can have so much information and yet be so dumb. One example (but I could give you many): I like cycling and I subscribe to some cycling-related YouTube channels (Lanterne Rouge, Dylan Johnson - normal stuff, informative, bits of light humor now and then). YouTube keeps recommending me one cycling channel I absolutely hate - it is as if it was designed to piss me off. Sensationalist, negative, clickbaity titles, made up doping allegations every other post, throwing up emoticons in titles, creepy thumbnails with syringes and distorted faces. I never watch those videos, I clicked "do not recommend this channel" multiple times, now I just leave YouTube immediately every time this appears. And somehow, with all the data they have on me and all that sophisticated AI, they still have not figured it out. How? Any explanation?
Everything is is by aggregate. So they can put you in a bucket with a bunch of other people with a similar footprint, and if 75% of people in that bucket convert when being shown that one you hate, you get to see it too.
Low-level optimization beyond that was rare at the places I worked.
"Sneaky but obvious" was way more common. And the browsers and platform vendors kept making it harder to do certain things, so it was a constant rat race to maintain the same level of browser tracking.
If that tablet company had very recently begun an internet marketing campaign, across multiple ad networks, target approximately your demographic, then it's wholly reasonable that you and your wife would independently see ads for it.
I think the thing that most people would really find tragic and scary is that we're all far more predictable and homogenous than we'd like to believe.
It's a low key way of chatting about huge datasets and the pattern matching they can provide to computers that we as individuals simply can't keep mental track of due to scale.
We are not as unpredictable as we all believe our tiny flower selves to be.
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.
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 :/
There's many other ways devices can be linked, addresses of bills for instance.
All the conspiracy theories out of the window...