BTC will flow from incompetent users to competent ones so concentration much like with other wealth is unavoidable.
Incompetent needs a bit more defining, to me incompetent owners of Bitcoin lose them to the benefit of the network.
My biggest fear is not selling but destroying my Bitcoins.
That is a concern but they aren't really destroyed. And when I say incompetent an example would be someone buying an ASICMiner with BTC that won't ever earn that BTC back and those BTC flow to ASICMiner shareholders.