The document discusses using Facebook as a subscription model for brands. Key points include: 1. Facebook can be treated like an email list, with metrics like list size, messages delivered, opens, and actions (clicks, engagements). 2. Community density analysis uses Facebook ads tools to analyze the interests of a brand's followers and their friends to score the quality and engagement of the community. 3. Growing the list involves using sponsored stories and ads to amplify content to friends of followers in order to gain more followers and community engagement. 4. Measuring the ROI of Facebook involves properly targeting ads, driving traffic to owned sites and domains, and analyzing both organic and paid traffic and conversions