It's called remarketing. If they're showing you an ad for a product you actually bought, they're doing it wrong. It's supposed to show you an ad for something you looked at, but didn't buy.

If it's not being done purposely for reasons others have mentioned, then I wonder if it comes down to the company's integration with Google. Presumably, Google wouldn't know if a sale took place unless the merchant somehow notified them. I'm guessing this might be with a pixel, script, or similar on their order confirmation page.

So, if the merchant failed to implement this, Google would never know to stop showing the ad.

No, the merchant stops bidding for the as once you complete the purchase.

Generally speaking, no. The cookie pools of users to retarget will be stored not by the merchant but a third party (either the company serving the ads, or a middle man). When a user gets tagged they'll stay in the pool of people to re-target either until their expiration date is hit, or until they are removed. So the merchant would have to notify (automatically) that a user should be removed, not just chose to stop bidding on that user.

Or they are trying to do the thing BMW and Apple do where they are trying to make you feel good about a decision you already made.

Or at least trying to avoid the feeling of being stalked you might get if their all-pervading ad-retargeting campaign that follows you round the internet for weeks after you first visit their website stops the day you actually buy.

Hey, if it keeps you from returning the product or avoiding a merchant, it has worked.

> ...after buying something I frequently see ads for the same exact product from the same exact vendor...

There is a theoretical justification for that (note: "theory" not used in the scientific sense!) -- for large ticket items like cars, recent buyers are more likely to notice an ad for the expensive item they just bought. Some ads are aimed at them to make the whole "experience" somehow better, to offset buyer's remorse. That way you will talk up your purchase and be more likely to buy another when you replace it.

The other is when you have a high volume low-price item (e.g. toothpaste): you've demonstrated a willingness to buy (i.e. you're a qualified buyer at some level) so why not try to remind you that the next time you need toothpaste you should get it from the same place?

Since so much marketing "science" is bull, nobody actually knows if this works (any more than they do with the online ads). But at least your seeing these time-wasting ads is intentional, rather than necessarily a software error.

Please make a difference between marketing and advertising. Advertising is a very small part of marketing "science".

That's a fair point, but I meant advertising as one of the tools of marketing (like datastructures are one of the tools of computer science). Sorry I was not clear.

Thus in my last sentence I was generalizing to say that marketing, even formal marketing analysis with statistics and A/B models, is still a mixture of heuristics, data, and superstition. And its practitioners

Since it's a kind of social science, I say that in contrast to fields like economics and psychology which also have plenty of charlatans but whose major practitioners are well aware of, and discuss, the epistemological flaws that still remain in the foundations of the fields. By comparison most marketing "theoreticians" remind me, at best, of alchemists.

There's no question that marketing is crucial to any successful business. But we have to realize that it's typically simply just gut judgement.

I don't think gut feeling is accurate. There is a popular saying that marketing is about applying a great deal of common sense. I think that's a bit more accurate description.

In any case, there's plenty of exact science in marketing dealing with statistical modeling. Then you have pricing, which is arguably the biggest part of marketing (a lot of people don't realize how much thinking goes into a pricing strategy). Then you have communication in all of its marketing forms, and lastly you have the product creation, which in itself is part of the marketing.

I view it like operating a jet. I have access to lots of buttons, switches and dials, and I know the science that takes care of what's beneath them. But in the end, I'm only interested in what happens as a result of using them.

There was a time when I could use a search engine to get a bit of information about something and then move on.

Now? That one minute websearch will stay with me for weeks as people push ads for things that I have no use for.

Prosthetic testicles for dogs; specific terms used for bras; packers and binders - my search history gives me a variety of eye-popping adverts.

Also: they really need to let people opt out of some advertising. People with alcoholism might not want any alcohol; people with OCD might not want cleaning products on a TVOD page about OCD (real example. I'd post an image but it's on the other computer).