People should in fact never give away Vent information to people who claim to be guild mates. If they really are guild mates, they can log on their guilded character and get the vent info out of the guild information section.
If they are not guild mates, they will act upset and hurt (a common ploy) that you don't trust them, and won't get in to our vent.
If they really are guild members, they won't have a problem logging on to their guilded character once you tell them where to find the information, and they will appreciate you keeping our vent info a secret.
Officers: I'd be extra wary of new applicants. If they really want to grief us, they may go as far as applying to the guild to get a peek at our guild info.