I've found serveral caches but most of them I doubt if they where hidden with permission. Cemetaries, national forests, under bridges, I doubt it if our government gives permissions. They don't want to be responsable if something happens.
And about responsability, what about the risk of finding the cache. I want to hide a cache under water. But what if some falls into the water when he's searching for it? Am I responsable? The owner of the land where it happened? The man who gave permission? Or is geocaching at own risk, like all other outdoorsports?