Rosenblum's First Law of Chocolate

Rosenblum's First Law of Chocolate (from a book on the craft of chocolate-making) states:

The more someone refuses to talk about what he does, the more he is likely to be involved in a lousy product.

The application of this in fields far removed from confectionery should be self-evident. Obviously, though, there are at least two fields where the opposite is true: espionage and Christian evangelism.