facebook can make you fat
So far, social networking sites have been talked about as new forms of communication, and it's been recognized that they're an important new ecosphere for the spread of memes/ideas/culture.
But it's only now that evidence is emerging for their ability to affect real world behaviour. An academic study in the US found that obesity spreads from person to person via social networks. Another found that a person's decision to stop smoking is strongly affected by what their friends and contacts on their network are doing.
The power of social networks to influence what people actually do is exciting - how much a influence a brand or government can exert on any particular form of behaviour via these channels is another question.
