Part of a part of one of the cases you have there is to do with barrier to entry. If a community has no barrier to entry, it can be vandalized for free. The ba

Part of a part of one of the cases you have there is to do with barrier to entry. If a community has no barrier to entry, it can be vandalized for free. The barrier could be the understanding it takes to navigate, a literal price, or knowledge of its existence. Smaller communities speak in ways and on topics that outsiders don't understand, and so outsiders are deterred. As the community becomes larger, it becomes more general, and so outsiders have an easier time integrating. When a community takes a price, vandalism has a cost, which is often not worth paying. (it could be something as trivial as be in a place at a time, or buy roller blades). Plus, there's definitely a tipping point beyond which it'll spiral outwards.