Well, I agree that for the most part consumers try to minimize their exposure to advertising, but not always. Some extreme examples of commercial advertising that was or is highly sought after by its target audience include eBay listings, Craigslist posts, the Yellow Pages, classified ads, the Sears catalog, job offer postings, the McMaster–Carr catalog, Computer Shopper before the internet was widely accessible, and "product reviews" by reviewers who got the product for free. So it seems likely that there would, in fact, be "ad speakeasies".

But let's consider the other side of this:

> I don't understand why you and others see this as a hard law to [...] enforce

Suppose we consider the narrowest sort of thing we'd get the most benefit out of prohibiting, like memecoin pump-and-dump scams, which are wildly profitable for the promoters but provide no benefit at all to the buyers, so nobody goes looking for. We can get a preview of what that prohibition would look like by looking at the current state of affairs, because those are already illegal.

And what we see are fake Elon Musk live streams with deepfaked mouth movements, fake Elon Musk Twitter accounts that reply to his followers, prominent influencers like Javier Milei for no apparent reason touting memecoins they claim to have no stake in themselves, prominent influencers like Donald Trump touting memecoins they openly have stakes in, etc. I haven't heard about any memecoins making ostensibly unpaid product placement appearances in novels or Hollywood movies (probably crime thrillers) but it wouldn't surprise me.

How about sports stars? Today it's assumed that if a sportsball player is wearing a corporate logo, it's because the company is paying him to wear it. Suppose this were prohibited; players would have to remove or cover up the Nike logos on their shoes. Probably fans would still want to know which brand of shoes they were wearing, wouldn't they? Sports journalists would publish investigative journalism showing that one or another player wore Nike Airs, drank Gatorade, or used Titleist golf balls, and the fans would lap it up. How could you prove Titleist didn't give the players any consideration in return?

A lot of YouTubers now accept donations of arbitrary size from pseudonymous donors, often via Patreon. In this brave new world they would obviously be prohibited from listing the donors' pseudonyms, but what if Apple were to pseudonymously donate large amounts to YouTubers who reviewed Apple products favorably? The donees wouldn't know their income stream depended on Apple, but viewers would still prefer to watch the better-funded channels who used better cameras, paid professional video editors, used more informative test equipment, and had professional audio dubs into their native language. Which would, apparently quite organically, be the ones that most strongly favored Apple. Would you prohibit pseudonymous donations to influencers?

Commercial advertising is in fact prohibited at Burning Man, which is more or less viable because commerce is prohibited there. You have to cover up the logos on your rental trucks, though nobody is imprisoned or fined for violating this, and it isn't enforced to the extent of concealing hood ornaments and sneaker logos. But one year there was a huge advertising scandal, where one of the biggest art projects that year, Uchronia ("the Belgian Waffle") was revealed after the fact to be a promotional construction for a Belgian company that builds such structures commercially. (I'm sure there have been many such controversies more recently, but I haven't been able to attend for several years, so I don't know about them.)

Let's consider a negative-space case as well: Yelp notoriously removed negative reviews from businesses' listings if they signed up for its service. We can imagine arbitrarily subtle ways of achieving such effects, such as YouTube suggesting less often that users watch a certain video if it criticizes Google or a YouTube supporter (such as the US government) or if it speaks favorably of a competing service. How do you prohibit that kind of advertising in an enforceable way? Do you prohibit Yelp from removing reviews from the site?

Hopefully this clarifies some of the potential difficulties with enforcing a ban on advertising, even to people who don't want to be advertised to.