When I take over a Barbarian camp with a captured worker from another nation, I have the option to return them or keep them. Returning them helps the relationship with the nation, keeping them is obviously labor for free.
How much is returning the worker really worth on the long run? Especially in the early game when I am short on workers it always seems best to keep the worker for myself. Is one decision generally better than the other or does it depend on the situation?