According to Guardian's Paul Lewis, social media can help journalists:
1) Finding people - crowdsourcing the pubic for information on the whereabouts of witnesses or other key figures in a story;
2) People who self-publish – activists (holding regimes to account), bloggers or anyone in need of a voice who would otherwise not be given a voice;
3) Big events – the London riots was an excellent example of how journalists could harness the power of Twitter to follow leads and chase down stories. The ensuing chaos was too big and too fast-moving for journalists to manage on their own;
4) The butterfly effect – a small action creating a ripple effect. It has to be a tweet containing very valuable information, which can be hard with 140 characters.