Regarding chicken bones, they're dangerous to humans mostly because they're so small that you can easily eat one by accident if its hidden in a mouthful of meat and you don't chew as thoroughly as you ought to. The same bone that might send a man to the emergency room would be easier for a cat to notice in its mouth, being significantly smaller. They'll still probably swallow it, but they're crunch it down first so that it's much less fish-hook-like in appearance going down the esophagus. Uncooked bones are less dangerous still, as they're not as brittle.