The possibility of being manipulated by big players: the institutional investors and governments. If governments and big corporations own large portions of Bitcoin, they can drive this market upside down, as they are already doing. Bitcoin should be better distributed among more different hands of independent individuals, instead of belonging in large portions to governments' wallets and corporations.

In my view, that is the biggest weakness of Bitcoin. That is how the centralized parties subvert Bitcoin's initial purpose, which was to give more freedom and independency to common individuals who have never seen their interests satisfied by the groups of power which rule life in society.