This command would reveal the administrative and technical contact people, who can find out what user owns the infringing files. Different databases have to be searched for different domains, but the contact people of any domain can be found. And since these contact people give out user accounts, they can find out who put any document or program on their systems. They may thus be able to follow the letter of the law while almost completely eliminating administrative costs for themselves and Internet services. But we all need to work together and think creatively to prevent this law from running away with us.
Nobody wants to put unnecessary barriers in the way of offering Internet content.
And it would be anathema to most Americans to force anyone to file a form just in order to provide information.