I disagree with your assessment. For one, if you base reliability on monetary costs, then it's trivial for a fly-by-night scam to work around it. You just have to get more money. A loan could work. Or VC investment - such companies have plenty of money to burn on advertising, and it in no way reflects the quality of their work.
Two, reputation. I don't think reputation matters much to anyone anymore. Think of all the corporate scandals that are featured essentially weekly on HN. Or, closer to the topic, think of all the bullshit newspaper publish that gets thoroughly debunked in discussion threads around HN or topical subreddits. And yet both those corporations and those papers are still happily chugging along, no worse for the wear. If reputation of news publications mattered at all, nobody would post anything from Bloomberg here ever since the Supermicro fiasco.
IIRC there was a similar phenomena with the dot-com boom: companies that spent hundreds of millions of dollars on advertising did so because they weren't selling anything useful, while the actual survivors spent zero on advertising and grew virally from word of mouth. Google and Facebook make money by selling ads, not by buying them: Google's first ad didn't run until 2010.
Of course there are projects that seek to archive online newspapers too (archive.org is awesome!), but online newspapers are able to thwart archiving either through technical means or policy (robots.txt.) Furthermore even when they aren't maliciously attacking archival efforts, online publications can swap out headlines or even the full content of articles, sometimes before the original has been archived. That sort of undisclosed on-the-fly revision simply isn't possible with print newspapers.
Also, the print newspaper industry isn't as clean as you think.
http://paulgraham.com/submarine.html
You shouldn't be trusting any ad, wherever it is. Actually, the most reputable the platform, the more skeptical you should be since you are more trusting of the platform to begin with. The easier you are to be duped.
An advertisement that happens to reach someone who has a problem that your product solves isn't a scam. It is a way to get that person to know about your solution.
It's like a city was proposing to limit car movement through the center to improve air quality, and you countered with "but some cars are electric and don't pollute!". Yeah, right. Wake me up when most of them are.
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[0] - See this subthread: https://news.ycombinator.com/item?id=21348886.
did the creator of the X pay a third party to present X? is X an essential part of its context? is the recipient of X seeking X itself or something else?
I don't think the parent poster meant absolutely all ads, just the vast majority of them. But in so far as they meant all ads, it's still a good point you shouldn't trust them - not even the product catalogs you yourself paid for. There's very little legal and social protection from the merchant lying to you, and all the business incentives to do so.
No fly-by-night scam operation will be able to afford a full page ad in a reputable magazine, and I hope newspapers also do due diligence on the advertisements they run, as their reputation (and possibly even legal liability, especially in certain fields like medicine, etc) is at stake.
This means I can be confident an ad in a magazine won't be an outright scam and I can somewhat trust it (sure, it's still trying to sell me something that I wouldn't have otherwise bought, but if it's relevant and I'm confident it's not a scam or low quality crap, then why not?).
The same does not apply to digital advertising where there's plenty of shit, no human actually reviews the ads and given the ads are very targeted there's little chance anyone else sees the ad (in a magazine, everyone sees it, so an expert in the field can speak up, unlike for a targeted ad where only the people in the targeting criteria - who often lack the knowledge to make an informed decision - see the ad).
The other advantage of the lack of tracking is that I get exposed to ads outside of my daily workflow. I work in IT, and if I were to browse without ad blockers (cancer blockers as I call them) I would just see IT or business-related ads all over the place. I don't want to see those - I already know what products I need for IT and have the knowledge & experience to do my own research. On the other hand, a print ad which knows nothing about me might show me an ad for cat food - I want that; I know nothing about the subject and am willing to trust the magazine's reputation behind it.