I seem to recall some previous posts on other threads where people have stated (in different wording) that "I shouldn't have to obey that rule because I didn't see it posted on a large sign with big lettering when I entered the campground or outside the office." Seems that the in-your-face signs are meant for these kind of people.
I don't think the vast majority of campers need the rules because they are reasonable people. The few obnoxious, me-first types need these rules posted so the camp owner or host can point to them when they have to trudge over to their site and explain that they are violating the rules.
Steve
