I don't know if that's it at all. I think the more likely explanation is that all of these companies are competing for a single, finite resource: human attention.

Maybe the opportunities for developing new ways to exploit human attention are simply drying up. Between streaming video, games, social media, podcasts, and just plain old traditional media (TV, radio, newspapers) how much more room is there to grow?

If I'm right this could be the signal of the current tech bubble finally bursting.