Audible signal to pass is the law in some states (including Ohio). In motorized vehicles most people ignore it except on one-lane roads. When I mentioned this being the law, someone here thought it was "nonsensical." I don't think so at all. I agree that it's common courtesy regardless. If there's a peloton, no, every rider doesn't have to call out, but the point rider should say it's a peloton. If I'm point in a small paceline, I'll usually call out in advance, and then when I'm beside the person, I'll tell them how many riders behind me.