It is hard. Very hard. A bitcoin address is basically the hash of a public key. It's trivial to prove that you are the owner of the address. Once you use name

It is hard. Very hard. A bitcoin address is basically the hash of a public key. It's trivial to prove that you are the owner of the address. Once you use names instead of addresses you need a mapping of names to addresses. Who owns a name? Who determines to which address a name maps? The namecoin project is currently trying to solve this problem (and doing exactly what you suggested), but there are still lots of potential issues.