I. The rise of the platform age -- The Internet: where are we now? -- Platforms: definitions, history, and economics -- II. The gang of four: the leaders of the platform age -- A mere bookstore no more -- Beyond the computer -- The king of social -- From search to ubiquity -- III. Synthesis: understanding the power of the platform -- The DNA: platform components and characteristics -- Gimme the prize! The benefits of platforms -- Slings and arrows: the perils of platforms -- The How: tips for building a platform -- IV: Looking forward -- The candidates: today's emerging platforms -- Coda: a glimpse of what's beyond.