Theories of social media influence come in two major flavors, writes Geoff Livingston. Some theorists hold that select influencers have the capability to make an idea spread, while others hold that viral ideas arise from the will of the crowd. Understanding the dueling ideas of theorists such as Malcolm Gladwell and Duncan Watts can help you figure out the right strategies for your brand, Livingston writes. "No one knows what's going to go 'viral.' But talking to the few and the passionate -- your influencers, often leaders in the community -- is always an ingredient," he writes.