Earlier quoted context omitted.
I wrote a reply but since it became too long, posted it as a comment: https://news.ycombinator.com/item?id=37266563
That was an interesting comparison of behavioral vs non-behavioral ads, thanks. But my question was geared towards the value of advertising itself, in general (if there is any). I am aware of the unknown unknown problem you mentioned (I think), but in my experience as a layman, very very rarely (if ever) was I introduced to a great product or service through advertising that I wouldn't be aware of in other ways. Conv…
Regarding your experience, a lot of advertising is retargeting or keeping the brand alive in the minds of buyers or remind them constantly (since humans are forgetful). This statistically increases the probability of purchases made amongst a cohort (very measurable). Personally, I think this is user-hostile and is a strong case for having more control over the kinds of ads we're exposed to or limit/penalise harmful ones. Taken to the extreme (going on a slight tangent here), if we really owned/controlled our devices and software, which means having control over consumption, we'd block all ads which would incentivise platforms to remove the distinction between content and ads and we'd do more content filtering on the client (This is however computationally inefficient, a sort of arms race).
Regarding influencing behaviour, it's a lot more efficient to match the right seller to the right buyer rather than influence buyer behaviour (which is hard). However, to achieve that extra marginal gains/returns on ad spend, advertisers often do attempt to change buyer behaviour (through building brand associations, retargeting etc). Again, better user control would help here.
Agree on street ads and other public real world ads as there is no consent here (Real world movement is a need, not a choice).
Regarding ads vs word-of-mouth, Ads really are very effective for many people, in a measurable way, both quantitative and qualitative. It of course will differ from person to person.
Regarding increased inefficiency and effect on the economy more generally, ads actually increase efficiency in the system as long as they are not rent-seeking (i.e. pay to jump the queue) or user-hostile. Eg: It helps many niche businesses reach customers which are otherwise very hard to reach (due to geographical or novelty constraints). Taken to the extreme, all value gained from advertising will ultimately flow to the ad platforms. Even in this extreme case, overall consumption increases (due to buyers buying more) as well as competition (due to many more competitive small businesses, innovators dilemma theory) which is good for a capitalist economy (i.e. makes it more dynamic in both choice and inequality) and increases GDP (a poor metric).
As an aside, it's also a progressive tax (I.e rich and poor both consume the same good but advertisers pay more to reach the rich, thus funding the good for the poor).
Some extreme opinions below on the fundamentals:
Even in localist/anarchist/decentralised utopias, ads won't die (especially personalised). It's a fundamental need of humans and the only other form of payment (apart from paying for compute itself) that doesn't depend on a system of violence to enforce it. As long as there exists economies of scale, there will be marketing (to increase consumption and hence cheapening it per capita i.e. use less labor), and hence advertising (to solve the unknown-unknown problem or presenting/impressing).
i.e. Even when we eliminate competitive enterprise, build localised production of needs, and have full control of our devices, if we want to build something cheaply or spread an idea, we'd have to advertise. It would look a lot more like "advertising on the merits" with full user control though considering human nature, there will also be a lot of "advertising focused on presentation".