Having the MAJORITY (51%) of the hashing power, more or less ends the currency, doesn't it?
No. The effects of a 51% attack are only temporary. As soon as the attacker stops attacking, or is overpowered by legitimate miners, the network will instantly resume normal operation. Some people may have been ripped off the attacker's double-spends, and everyone will be forced to temporarily stop accepting bitcoins to avoid becoming a victim of a double-spend themselves, and the exchange rate will likely take a massive hit as many people lose confidence in the currency, but apart from that it'll be as if nothing ever happened.
Apart from that? That is quite a lot actually.
What will get the attack to stop, other than defeating it?
So a hashrate / difficulty increase is a call to arms for those that would defend the currency.
The army of gamers and their GPUs can be called on via bitcointalk and STEAM and WOW (or whatever game might be popular now) to leave their raids and get to mining instead. That is our bitcoin Paul Revere
These gamers are our minute-men and women.
The alerting and alarming systems should be prepared and tested if we are going to expect them to be effective.
