Honesty?

Why be honest? You could be honest to get something in return or to avoid something unpleasant. You could also be honest because you hold it as an important value regardless of whether you get a return. Most people will know when a compliment is sincere or expecting a return. Honesty and trust are close mates. If you want to be trusted, be honest because it is a very important value and not negotiable. Expect nothing in return.