> but if a minor is caught using someone's credential, then the person whose credential they are using can be investigated, and, if necessary, charged with a crime roughly equivalent to providing alcohol to a minor. Without the possibility of real world enforcement, none of these identity solutions can possibly work.
They don't work even then.
Suppose you completely eliminate privacy on the internet and require every domestic site to collect the name and social security number of everyone who visits. Then a child uses an adult's ID, regardless of whether it's with or without their knowledge. Is the child going to inform on themselves? No. Is the adult, when they don't even know about it? No. Is the adult, when they provided it on purpose? No.
That constitutes the entire set of people who would typically know that the person using the device isn't the person on the ID.
On top of that, we can punch an even bigger hole in it. Search engines, among other things, index other sites. Google is obviously the biggest but there are many others -- Bing, Marginalia, Brave, Swisscows, Yandex, Perplexity, Baidu, etc. They're run by adults and most of their users are adults, who reasonably expect to be able to turn off "safe search" if they want to. So some adult at each search engine would have to provide their ID to the crawler so it can index things inappropriate for children and show them to adult users. It would therefore be a fairly unremarkable and recurring thing to see the same ID make a zillion gigatons of requests.
But then you can't use "why is this person downloading 100 things from 100 computers at once" as an indication of anything nefarious happening, and anyone can still set up a service hosted on a foreign server that will serve adult content to anyone without an ID by serving it out of a cache. (And in the case where you're invading everyone's privacy, that service would also be very popular with adults.)
> Is the child going to inform on themselves? No. Is the adult, when they don't even know about it?
In the context of social media, if they want to actively participate they have to given that it's the entire point. It's true that even with a government ID scheme people could borrow someone's ID to get passive access with their consent. But a kid couldn't share an account with a parent without that parent knowing because you see their activity, and they also couldn't post.
> In the context of social media, if they want to actively participate they have to given that it's the entire point.
If the kid signs up for e.g. TikTok and the adult neither uses nor has any intention of using that platform, what causes them to even notice that it's happening?
Social media also seems like a pretty obvious case for this not working at all because if you ban kids from the ones based in your country, they'd collectively sign up for one based in a different country that doesn't enforce the ban, and the network effect for that age group shifts there because of the ban.
> It's true that even with a government ID scheme people could borrow someone's ID to get passive access with their consent.
That seems like the main problem though? Even if it actually prevented them from posting, you're conceding that it neither prevents them from doom scrolling nor accessing pornography, which are both passive consumption.