In fact, if used properly, it can be a powerful resource and career aid providing you with a great deal of useful information, especially rumors and opinions. Some people refuse to deal with the grapevine because they consider it gossip, irrelevant and beneath them, citing idle chatter which busy, hard working people don't have time for. Gossip can be an intentional leak of information that you should know. Conveying a superior attitude about the grapevine could eliminate your sources of information. Busy people are not necessarily hardworking.
Smart people make time to manage their careers.
Cultivating sources of information makes sense. Ignoring or discounting information could be disastrous to you and your career. Traditionally, the grapevine has served several useful purposes. It circulates information that, of course, allows individuals, or groups, to respond accordingly. To be caught off guard is very disconcerting.