Professional relationships are incredibly important to productivity. Workers who communicate in a personal fashion develop more trust and chemistry with their peers. But it's a risky venture when you cross the line from friendly conversation into gossip and rumor mills.
Gossip and rumors often poison entire offices. When fueled by rampant gossip, one half-truth or perceived slight can breed mistrust and hard feelings between co-workers and supervisors.
Keep in mind that, by its nature, gossip is often misleading or totally false. Participating in gossipy circles, then, just perpetuates problematic interaction that can hamper a whole group's effectiveness.
The good news is that you don't have to contribute to the problem. When other employees try to share gossip with you, politely change the subject or remove yourself from the conversation. Doing so doesn't mean you have to totally avoid informal topics with a wide range of people at work -- it just means refusing to participate in damaging or disparaging conversations that have no positive purpose.