Depends on the circumstances. As a provider, I expect that toys will wear out sooner, and that things will get broken. I have pretty much anything of value put up out of arms reach or in china cabinets for that reason.
I will admit that willful destruction of things is something that makes me see red. Even with my own kids, I go a little nuts over it, haha. If a child breaks something on purpose, as often happens when kids get jealous or just want to act out, they are spoken to once about respecting others belongings. After that, I would likely ask mom/dad to replace the item or it's cost somewhat. This is still MY home, and one of our primary expectations is to respect other people (thier body, feelings and property).