Large scale change is about the numbers. If part fo your strategy for large scale change is to develop or use networks to communicate your message then you need to understand the mathematics of networks.
If you don't know about Sarnoff's Law, Metcalfe's Law and Reed's law - then watch this video, which if nothing else, explains why broadcasting messages is low impact. It's 10 minutes long but hang in there - it's the best explanation I've heard for a long time.
Sarnoff: 1 message to 20 people: network score of 20
Metcalfe: Email and telephones connect humans and help small groups form: because everyone can connect to everyone, the potential is 20 x 20, meaning a network score of 400.
Reed: the value of the network is exponential in social networking, going beyond the establishing communities.. So it's 2 to the power of 20 which is 1,000,000.
Reed's Law is about scale.
Social networking matters.