this is a podcast from the bbc about how social networking sites have been used to connect mass audiences which have been used by countries such as Moldova to organise anti government rallies which brought about revolution in the small country. The use of social networks also aided in the siege of Syria, without the use of social networks, the atrocities being committed in syria would not have been known to the rest of the world.
there are also risks with using social networks such as a woman was murdered by her boyfriend after he saw a photo of her with another man on Facebook and it can also effect work lives because some people post innapropreate information on their profiles which can impact them. The use of networking sites is also embraced by companies for advertisement when they set up pages for people to join where they can post special offers of pieces of work.
a problem with some social networks is that the items posted become property of the network for example everything posted on Facebook is owned by Facebook so anything you say or post becomes their property which people are tying to combat.