Chocolate I think seems to be the food that most people are aware of when it comes to feeding their dogs, and even if a dog might like chocolate then it's a good that's a definite no no, and is practically poisonous to a dog's digestive system. The chicken bones though I think a lot of dog owners won't be aware of, and they'll just think that any bone is ok for a dog to chew on, but that's not the case at all. Chicken bones, when bitten into, tend to splinter and that can then either get stuck, or even cut the dogs mouth or throat.
That's also one of the main reasons it's important to make sure you train your dog's not to go through the household trash, as just because you might not give your dog a food, doesn't necessarily mean that they're not going to be able to sniff it out and help themselves, and I'd suggest that in most cases then that's what's happened. The dogs have found the food rather than been actually given it.