Open worlds can be destroyed very easily. People can edit like other worlds, only without the code, so all it takes is one person looking to vandalize. The creator may be upset if this happens. Open worlds are harder to spam because you have to keep clicking.
In locked worlds you need the Super secret edit key to vandalize. When somebody gets the super secret edit key they may destroy right away or just plan to destroy. The creator may make a Code Is World which are much easier to destroy than open worlds. If a creator leaves a world, it may still be up if others are in which can lead to vandalism. And do not use certain edit keys or show it on the map.