I have been thinking, if Bitcoin relies on processing speed and processing speed doubles every two years… consider the following:
2 year worth of dehashing(proof-of-work) in 2010 is symbolized by 2Times2010
2012-14: 4Times201014-16: 8Times2010
If in 2018 somebody wanted to change who owned the first bitcoins, he or she would need 2Times2010+4Times2010+8Times2010+16Times2010= 30Times2010, which is 2Times2010 less than what one would get by turning the whole bitcoin network against itself for 2 years(2018-2020), in fact that remains true no matter which year one picks: someone in 2060 would need to turn the bitcoin network(or network of equivalent processing power) for 2 years too. The fact that bitcoin is growing faster than 2 times every two years worsens that math(requires less present time to beat past recordings). Think about it, if in any two year period down the road the internet(or the people controlling present processing power) decides that bitcoin sucks: bitcoin is gone.
We have elected fools for longer periods of time for the most powerful posts in the world. Doesn’t sound promising.
Of course, this attack is largely theoretical and doesn’t minimize current usefulness in having an electronic medium not controlled by any government. I think that if bitcoin falls it is going to be replaced by something similar.