Agreed, that is positively nudist etiquette. One person said that someone should sit if they are sitting. The problem becomes if someone is walking the beach, they don't normally have their towel WITH them. It's normally on their chair, unless they planned on sitting down somewhere else. So the person often ends up standing, which is what we do, unless someone INVITES us to sit on their towels. I don't really see this as a big issue. Seems pretty common sense.