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

What is Rumours?

Rumours is :

- A currently circulating story or report of uncertain or doubtful truth.

- A piece of information whose truth or source is unknown.

Rumours can easily affect people's reputation. Example if a news report says something bad about a celebrities that you like, you might slowly dislike him or her for being like what the report says.

In some cases, it's difficult to tell the difference between gossip and a rumor. Some people tend to mix up between rumours and gossip. Because gossip spread between friends, sometime sounds like rumour.

So..
What's the differences between rumour and gossip?

While disseminating rumors helps social webs determine whether a report might or might not be true, gossip is a whole different tale. It doesn't necessarily matter if gossip is true or not. Its goal is to change and maintain clusters of people, either by shifting around a social structure or spreading ideas about what is normal behavior. Gossip also brings people closer together.

Gossip sounds something like this: Did you hear what Joe did at the company picnic last week?

The gossiper hints that whatever Joe did, it wasn't a good idea and his performance violates a social norm. As well, the gossiper is taking a risk to voice her disapproval about Joe with the listener, forming a connection between the gossiper and the listener.