I'm wondering about the usefulness of the Cultural Bomb. It may be useful against indipendent cities, but I don't understand how to employ the GA in a war against a Civ. I am sure there is a way, though.
And usually, if your borders are so close to the city's one, it's easier to annex it than to use the CB.
It's useful for getting the other AI to declare on you, rather than you on them so you can reduce the amount of damage to your reputation.