Influence marketing has become programmatic word-of-mouth, with Americans spending more time on social media daily than email and search engines combined. Influence marketing allows brands to leverage consumers driving the most social engagement from their friends to create and distribute content at scale and drive ROI. There are four critical factors when choosing social networks for influence marketing campaigns: reach, social relationship strength, content structure and half-life, and search engine signals. Everyday consumers and niche communities typically yield the best results for influence marketing.