I have had this discussion many times. In normal wind conditions the wind will keep the boats off. At some moorings such as the Rhone when I pick up a ball it might be 5 feet off your stern, but once I load it, we will be 25 feet apart.

I have had on one occasion in a no wind condition a boat swing into me as odd currents then prevailed and we ended stern to stern. But generally in no wind, the weight of my bridle pulls me up to the ball (tangling around the ball). Or just ball will just bang on your hull.

Now on the balls at the Caves at Norman it is a different situation, with the current and swirling winds boats bump there often.

I find some people like to scare others off for privacy. If I found a boat coming in to anchor or grab a ball too close when I didn't want company, i would just start showering naked, that would run them off to scratch their eye balls out.