I think there was another thread that touched on this recently... As I mentioned there, I have a tough time with things getting broken or trashed. Even with my own kids and their belongings. BUT- it is part of having a home daycare. The sheer volume of children playing with things all the time means they wear out faster.
Having said that; I have no tolerance for being reckless with any of our belongings, or my home. We don't jump on the furniture, smash the wall with toys or "crash" toys into each other with undue force. That is something I crack down on immediately.
I don't know that you can really approach the parents for it. How easy is it for a kid to say "It was an accident! I didn't MEAN to!"? Very.
I also get my kids to keep anything special in their rooms (no dck allowed). And I have to say, if they forget it in the playroom or living room, it's fair game.