Advertising is only able to exist when there's centralized entity controlling the presentation of the content. TV and radio are good examples — your receiver simply plays whatever is on air, and has no idea what's in there. Social media services like Facebook strive to control the experience end-to-end precisely because of that too, and that's the reason why public APIs for Facebook and Instagram got reduced from "enough to build a third-party client" to "you can post, getting any info for the current user requires a manual review, and you can't do anything else".

Contrast this with email and phone, the only successful federated systems. Spam is illegal in some countries, and there's a concerted effort by everyone to fight it.

When no one controls the whole experience end-to-end, there is simply no technical possibility to expose you to something against your will. This is why decentralized social media is the future. I just can't see how Facebook could survive much longer unless there's a drastic change of some sort.

I dread to think what happens when ads collide with cryptocurrencies. They’ll either wipe each other out or merge into something far horrible.

They're already dating and it looks like marriage is afoot. Plenty of ads driving people into crypto scams.

Isn't that basically what Brave is doing with Basic Attention Tokens?