Ditto. I'm being bombarded by airbnb ad (on all possible platforms, e.g. facebook) recommending the exact same house I've already stayed in a few weeks back! Just stop...

You can avoid much of these issues by browsing in incognito or private mode when purchasing or looking to purchase or something. You can make your life a lot easier using firefox containers + container addons that automatically switch to isolated site-specific containers when browsing ebay or amazon or even facebook. Otherwise you're just inviting all kinds of cookies and tracking without making even hard for them

The point is that the ads are a waste, and that the advertisers aren't getting their money's worth. It's really remarkable that they still haven't caught on to this.

The ads are not a waste. It's called remarketing and it does boost conversion numbers over raw untargetted ads. The ads are targeting people who went to a site, browsed around, didn't buy but might do in future (much more likely than a random unselected person).

Generally the ad network does not know if you really completed a purchase or dropped off during the funnel. Presumably advertisers could set up a hook to inform the ad network if you did purchase or not, but I guess they don't care enough to do so.

Is there even a way to check if the google and facebook charge the correct number of advert impressions? Seems to me like they can print money by reporting higher numbers.

I haven't played that game in a long time, but back then they were the sole determiners of whether a "click" was valid or not. I got charged for clicks for which people only stayed for a second or so. Now there were a lot of people who claimed they can make a decision about purchasing from a website in a second, but I don't think they're thinking it through. I think they were erroneous clicks or competitors, yet I was charged.

They may have improved.

Even at big tech companies, a lot of those ML models are fed by nightly jobs, so updated once a day. If the targeting occurs on an outside property, there may be more delay. So if you make a purchase on day X, you should expect to see the ad for another ~48 hours. That's assuming there's logic which actually de-targets you post-purchase.

Even Amazon don't get this right and should have unbeatable knowledge of when the sale completes. Their helpful suggestions still only seem to work usefully for books and music.

I suspect that's because those are the only things that are easy to model. People buy them: a) based on personal taste b) in volume

I just bought a ladder on amazon, what information does that tell them? Since it's the only tool I've bought from them it doesn't tell them much. They now know that I might be willing to buy more tools from them in the future but doesn't help in targeting which kind or how often. Me being a ladder buyer is a very weak signal that I will buy any particular item from them.

If on the other hand, I've bought 15 Aubrey Maturin books from them over the last few months, it doesn't take the most sophisticated model to determine that I probably want to buy number 16 next. Or that I might like to read the Horatio Hornblower books.

Many people click on those ads due to buyer's remorse. Advertisers pay for clicks, and get what they pay for.

I suspect the odds are well above normal that someone is going to buy a second _. At a minimum _ shows up and doesn't work pushes things above buying for example a vacuum cleaner on a random day.

Do you want the merchant to tell advertisers you've bought that product?

Amazon knows I just bought a fridge. How many fridges per month do they think I need? I keep receiving fridge ads and even on their own website, when logged in, they show me fridge offers.

Perhaps the intention is for the purchase to stay fresh in your mind so you're more likely to mention it to other people?

The ads drove you to post here and as a result, I'm reminded amazon is an option for white goods.

Taken to an entertaining extreme, one advertising approach would be to make ads as noticeably terrible as possible so people complain about them as much as possible.

It's almost as if, no matter what these advertising networks do, you can always reason in hindsight that it profited someone ...

It's almost as if, because it's rumoured to have powerful, dark & unknowable Machine Learning behind it, people assume it must be doing something reaaaaaally clever, and we're just not clever enough to realise what it's truly masterminding.

You're right in the specific case of Amazon and that product type: their advertising should definitely be more intelligent in that case.

more often than not, the merchant is the advertiser.