The problem with opening the "which obscene is protected" door is that it gives the government (presumed to be correct in judgement by default) too much power.

The problem with opening the "which obscene is protected" door is that it gives the government (presumed to be correct in judgement by default) too much power. See Bush W admin's leaning on credit card processors to freeze out content they didn't like. If a Miller bargain must be struck, then "not allowing pornography to be exposed to minors (and no other limits for everyone else)" seems a better line. Then putting some safeguards in around what can and cannot be used as an age test in order to maximally preserve privacy (e.g. independent, non-government company, no identifiable information persisted, non-id verification options, etc) and what constitutes pornography (and what isn't). I'm a free-speech maximalist, but "porn for kids" is a tough hill to die on. Even if there are sound technical reasons why that should be allowed, there are too many social ones to make that the all-in bet in a democracy.