[UweSchmidt]

Bitcoin could become a means for payment and other things, but can not possibly replace the current systems of currency, since those are essential political instruments.

Consider the impact of minimal fluctuations of exchange and interest rates. No one could just say "fuck it" and buy into a completely unpredictable new system. Governments would give up control, and random people who happened to have mined Bitcoin until that point would hold the world's wealth? I don't think so.

[fennecfoxen]

Governments have given up control before... small governments, where after running their existing currencies into the ground with hyperinflation they adopted the US dollar.

Currencies can only be political instruments up until a point -- and then people get tired of it and start looking for other mediums of exchange, units of account, and stores of value. Bitcoin is theoretically something people could turn to for one or more of those, though it would have to be a pretty bad situation to make Bitcoin's volatility look good.

(Disclaimer. The overall likelihood of this happening at a large scale is not something endorsed by this post.)