As you pointed out it all comes to stake distribution and a good will of token owner, however I wonder if it would be possible to code the governence in a way which would give back control over token back to the stakeholders. I can imagine, in this competitive environment more decentralized solutions would get advantage over these centrally governed.
And, the basic assumption is that each individual will act in a way that is consistent with his/her best interests (and also in accordance with his/her local knowledge).
I would hold this assumption valid only on some idealistic level, we are neither reasonable, nor tending to get perfectly informed, actually, it creates highly competitive environment, which rewards only the most engaged and oriented (very often insiders) creating conditions of stress and fear for the most. I don't believe this is ideal situation for social media ecosystem.
And there come another factors: changing social networks like your cereals? Dumping all your network of social contacts because another network grants you more power in decision making? It doesn't seem very humane. Financial is not only motivation here. I can imagine working this model on the cryptocurrency market, where decisions are strictly economic, but social dimension add whole level of complexity here.