In practice, I get the impression that the emperor isn't wearing a whole lot: It's really difficult to demonstrate that any particular ad campaign generates a positive return at all, let alone that any particular technique justifies its cost, or that something that worked well the first time someone tried it will continue working well once everyone is doing it. The whole space looks to me like a morass of wicked high variance, confounding variables for days, spillover effects, blah blah blah.

Combine this with marketers wanting to be more data-driven - and needing to report numbers to their own bosses - and you've got a situation ripe for exploitation. I expect the adtech companies could sell pretty much anything, as long as it smells like numbers.

You grossly misunderstand digital advertising or your bias has completed clouded your logic.

> A wedding anniversary is a significant thing–some John's may be swayed by an advertisement, but many would consider it a bit of a cheat not to put more "novel" thought into it.

No idea what you mean here by cheating or novel thought. We're talking about whether knowing that info allows you to have more successful advertising compared to random chance. Serving John ads for roses, chocolates, and vacations will be more effective than serving those ads to a random person.

>Frankly, the former of those two data-points could mean anything. Much of what advertisers believe about consumer habits of single people could easily be correlation.

Correlation is the whole point. If someone who is single and goes to the gym is correlated to certain purchases or behavior, you can advertise those. And being single, a woman, and a gym-goer isn't super valuable by itself but combined together you can advertiser women's athletic clothing that is functional but also attractive.

> As for the latter, anyone with a daily gym routine is less likely to want to change it. Selling gym membership to someone speculatively hoping to start going to the gym is a better bet, but much harder to track.

Again, you don't understand advertising. If I know someone goes to the gym every day I'm not going to advertise gyms to them. I'm going to advertise water bottles, protein, healthy meal kits, athletic clothing, etc.

> Going back to the anniversary gift—I seriously doubt many people are much swayed by one-off ads in buying something as significant as a car

We're not selling Steve a car with targeted ads. We're taking his promotion and propensity towards bmw to assume hes wealthy and likes luxury goods. You advertise more expensive goods to him, rather than cheap ones.