A prudent man conceals knowledge,
but the heart of fools proclaims folly.
Proverbs 12:23 (ESV)
I don't think this means that a prudent man hides things that people need to know, withholding important information.
I think it means that a prudent person keeps information carefully. He is discerning about what he shares with whom, and when.
He does not feel the need to show off everything he knows. He is secure and humble, and he does not depend on his ability to spread information to build his reputation. He does not shoot off his mouth.
A fool, on the other hand, shoots off his mouth all the time. He makes outrageous promises and claims. He passes on information as quickly as he possibly can, always wanting so badly to prove that he was First To Know that he often doesn't even take the time to determine whether what he "knows" is true.