Ben, one scenario you didn't think about...
How would someone determine who owns a particular site/domain? They would check the whois info, right? What would happen if a webmaster transferred all domains to an non-american business address/owner? The DOJ would have no jurisdiction for a records inspection. Maybe they could shut you down if they suspected you of illegal activity. But if you were doing nothing wrong and featured obviously adult models, I don't think they would bother.