I suspect that this article makes more sense if you've read his book, which hits on the same themes with a lot more context, and a lot more history.

Youtube optimizes for grabbing attention in well-defined bite sized chunks that people think they can spare. A little dopamine hit, followed by another, followed by another, followed by..why didn't I get anything done today? The interaction isn't meaningful. It isn't rich. It doesn't improve our lives. But it is addictive.

If you don't see what is wrong with this, I recommend reading http://www.highexistence.com/why-you-should-avoid-the-news/ until you think you understand it. Then re-read the article above with that in mind.