You might be right, BUT the key is that people can create competing platforms, even ones that have content that purposely disappears, like snapchat. Humans will find a way around whatever system is created. And if any system becomes too all-encompasing, it creates a massive opportunity for a competitor to gain market share simply by being an different option than the most popular platform.
I think you are missing the point here. If there are competitors, they most likely will mimic the voting responsible for the very success of the platform. That means the same possible issues Einar is talking about in this video and that is, will the success of this platform be paramount to a popularity contest where who we know is more important than the actual content. Another great point made in the video is how genuine are people's comments? Good video!