Scott Galloway, who is a professor of Marketing and Brand Strategy at the NYU Stern School of Business, did a presentation called "Gang of Four: Apple / Amazon / Facebook / Google." It's a lightning fast presentation on how these companies increasingly dominate the world, wield more influence, make all the profits, and affect our lives. I don't agree with everything he said (his thoughts on Apple's taxes in particular), but his insights are excellent. He's also a very entertaining speaker. I strongly recommend you take the 16 minutes to watch this video.