I hope in skyrim, it is possible to sell simple things like swords or shield or other regular items. But special items like horses or special weapons, armor should have some sort of ownership certificate. If you kill the owner, you could steal the certificate, or when you buy a horse, you also get a certificate. I could add something nice to the game imo. Also the thieves guild could provide in false documents...
It would be cool if you ask me. What do you think?