The author of this article is basically saying that Facebook is vulnerable to failure because the mass of people might leave and join another service. The reason for that happening would be to join a free and open network, but as I stated before (without evidence) most users don't care about a company owning their data anyway - so it's not going to happen.
I am saying the first part. I am not saying that users will necessarily leave because they want to join a free network. If you read my post (or even the little bit quoted above) you will see that I suggest that folks might also leave for a sexier proprietary service.
I care deeply about free and open networks and I'm actively engaged in advocacy to encourage other people to care about this also. I think, to differing degrees, many people do care about these fundmental issues. But I also think the real political implications of using particular technologies are pretty opaque to many users.
This particular essay was just trying to argue that suggest that people are being unimaginative if they throw their hands at the idea of Facebook's network effects. I hope it's eventual replacement is more free and more fair. But I don't think it has to be. It might very well be worse.