Number one use case is sending anonymized and hashed data back to the ad platform to trigger conversion events.

Essentially all modern advertising is done algorithmically. The platform takes conversion events (a typical event is "someone fills out a form"), that signal is sent to the platforms, and the platforms use it to serve your ad to other people who may be interested. GDPR as it is means you need opt-in to do this, so it greatly reduces the effectiveness of online ad targeting.

So in practice, say you make a new cool B2B tool for, say, plumbers. It automates your plumbing business and makes plumbers more money.

In the US, you can make a Meta ad campaign with broad targeting and Meta will use algorithmic magic and be able to just find plumbers for you to show your ad to.

In the EU, this doesn't work as well, so its harder to find plumbers to show your ads to. Less plumbers get to use your product as a result. So its just one reason it's hard to get your EU based Plumbing SaaS off the ground.

Biggest issue with this is the modern web ads don't even work.

You get ads for fridge AFTER you bought one since they now know you browsed them.

What works is content based advertising - so advertise a power drill on a woodworking hobbyist site. No tracking required there. Conversion can be obtained when user clicks a link via redirect. Like in the good ol times.

But this modern approach that massively invades privacy has been sold to businesses and now they require it even though it is probably ineffectual.

> GDPR as it is means you need opt-in to do this, so it greatly reduces the effectiveness of online ad targeting.

Good! I don't want ads to be a thing in the first place. It's a good thing that industry is being strangled by regulation.

Essentially all modern advertising is evil.

They are strangled by rules in using personal data on algorithmic advertismenet?

GOOD!