This is a question of forum etiquette.
Recently there has been some discussion about OBO. I don't mean auctions to the highest bidders. I mean that are we to assume that unless a person states OBO they are NOT open to receiving offers below their asking price? I was under the impression that every sale operated under OBO without the need to state this, since it is common for a seller to lower prices on an item that is not selling at their asking price. Is it rude to offer a lower than asked price if OBO is not stated in the listing?