How are rumours usually spread?

Mostly by Mass media.
- Newspaper , Magazine , Television , Radio , Internet [Facebook etc.]
- People

Let's say you've just heard a REALLY juicy rumor about someone you know. It may not be true, but it's too good to keep to yourself. Your first instinct is to hop online and share it with all your friends.
We've all had that kind of urge. But why?

Here are some possible reasons:

• To feel like part of the group
  If everybody else is gossiping or spreading rumors, you might feel you have to do the same thing in order to fit in. When you're "in on the secret," you're in the group. Unfortunately, the person who the gossip or rumor is about is usually left out of the group for the same reason that you're let into it.
• Out of jealousy or a need for revenge
  If you're jealous of someone's looks, popularity, or money, you might gossip about that person in order to hurt him or her. If you feel that someone's done something bad to you, or deserves to be hurt, making up a rumor might satisfy your sense of justice.
• Out of boredom
  Did you know that in many studies, this was the #1 reason why young people say they spread rumors? Sometimes, a period where everyone is happy and getting along just seems kind of-dull. Spreading juicy dish might shake things up a bit, or get two people to start a fight, and that would make life a little more exciting. All those tabloid newspapers and TV shows full of celebrity gossip are pure proof that rumors are a popular form of entertainment.
  
  People's view about rumours : "I think that people spread rumors and gossip because they are either bored, mad at that person, trying to stir up some activity, or to get attention."

Source : http://pbskids.org/itsmylife/friends/rumors/article4.html