From a technical perspective, Google could compare whois domain registration details and snapshots at the Internet Archive with the allegedly infringing URL.

There could be mandatory identity verification for filing DMCA complaints as well, but I'm not sure whether that would gel well with the current regime which penalizes not acting on infringement notices. Further, as someone whose application assets were copied without my permission by small time firms and had to go the DMCA route, I'd probably want to avoid giving out my ID to every hosting company under the sun.