To play devil's advocate for a moment, is this different from age-gating we do anywhere else on the internet? We require you to be 18 or over to look at adult sites or view particularly edgy stuff on youtube. Is the difference just that there's an implicit wink going on because it relies on the user being honest about their age? I'm sure if we had a real ID system like China in place, laws would mandate its use given US attitudes about porn and gore.