There was one time that I found bed bugs on arrival and took a picture (thank goodness I was able to escape without carrying any); they gave me a full refund + some extra inconvenience money (in cash, not airbnbucks). Probably would have been much more complicated if I had stayed a night or if I hadn't been able to get a picture / easy proof. But it was nice to have Airbnb as a 3rd party in that instance.