That does work for domains within Namecoin, but it cannot be used for ICANN TLDs. People have suggested pairing schemes to allow domains under other TLDs to be

That does work for domains within Namecoin, but it cannot be used for ICANN TLDs. People have suggested pairing schemes to allow domains under other TLDs to be associated with Namecoin records but I have yet to see one that is secure (they all rely on honest miners).