Just lose your paranoia, and learn how to make the grapevine your friend. It tells you how to turn your rumor mill into an ongoing focus group that enables you to tap into what your employees are really thinking and feeling. Don't be caught by surprise. Rumors often start because of misunderstandings, or because information wasn't communicated quickly and clearly. You can't control what employees say, but you CAN defuse their bombs by monitoring the rumors and immediately squelching false ones.
Every organization has informal leaders who wield real clout in the cafeteria and back hallways.
Do some digging and find out who these people are. Then seed them with the information you want spread around. Manage the grapevine well, and you won't have to worry about turning out sour grapes.