Legally? You lose the TiVo, with no recompense from Best Buy. You would have to sue the "thief" to get any money back. Now I agree that the chances that Best Buy would ever go after your TiVo are practically non-existent; it's not worth it to them either financially or customer relationship-wise. But if your TiVo malfunctions under warranty; I'd bet there's no way you could go through Best Buy to get the TiVo exchanged. Personally, I prefer not to buy stolen merchandise.