Fighting against regulations in the name of anonymity is the best way to actually harm anonymity. We can have both (while we currently have neither in practice …)
I'm strongly opposed to ID collection of any kind. But I think age bans are a good idea.
Why not sell age verification codes at physical stores? One code per account per website. It's good for 2 years and costs no more than $5. You can pay cash at the store and the sales clerk may only check your ID, as though they were selling you tobacco or alcohol. They cannot record anything.
There will still be straw purchases, just like booze and cigs. But it makes it easier to police the ban on minors joining social media without seriously compromising anonymity for adults. Few kids in my high school smoked or drank. Most couldn't access those things. And social media has network effects. If most kids can't join it, the rest probably won't bother.
This is why I can’t take any calls for banning social media for kids on HN seriously: The moment anyone introduced any legislation to limit social media access by age, this creates a de facto requirement to verify ID. The people in this thread would be up in arms as soon as the government tried to force companies to collect their ID to use social media.