Minority fork possibility

[natd]

 In an hypotetical case a  country government decides to control bitcoin by buying 80% of all BTC available. Could the minority (20%) rebel against it and fork the block chain? Can the rebels produce less difficulty blocks in order to overcame the majority stake?  I'm just wondering if that is possible.

[katoshi]

i guess it would be easier to just switch to an altcoin

[natd]

 Hmmm somebody thought of that already, and it seems possible: http://www.pcworld.com/article/2060840/selfish-miner-attack-could-devastate-bitcoin-researchers-say.html