There is a potential for danger in every situation. So no. I think that if someone is aware of the risk and takes it they are at fault should something go wrong. If I go after a cache and get hurt it would be my fault for tripping not the cache owner's.
Just a thought- people in the US have a 1/87 chance of dying in a car accident during their lifetime. How many caches are near roads? So in my opinion a cliff is no different.