Namedropper wrote: "So, if, say, someone sells you a name, lists you as the registrant, but doesn't give you control, as the a practical matter you don't really own it, as he can list anybody he wants to be the registrant at a moment's notice."
Namedropper, you are right. Practically thats true. In theory its just like nameslave said. The key thing is prooving your registrant/ownership status. And this can be done by contacting the registrar, who should track whois changes...