Quote from: socrates on December 12, 2012, 03:52:21 PM

When bitcoins threaten any major currency or the government control of economy, then they will have an incentive to make the 51% attack. That's when the chances of it happening go up.

I am still interested in knowing if there is anything in the technology that can thwart this.

Some would say that bitcoins already threaten all major currencies and the government control of the economy.

The technology is designed such that it becomes more difficult and more expensive to engage in a 51% attack as more people take up mining. There is a cascading chain of events here...

The more mainstream bitcoin becomes, the more people want it.
The more people want bitcoin, the higher the exchange rate and the higher the value of the block reward and transaction fees.
The higher the value of the block reward and transaction fees, the more incentive there is for miners to try to get some of that money.
The more incentive there is for miners to try to get some of that money, the more mining equipment that enters the network.
The more mining equipment on the network, the higher the total network hashrate.
The higher the total network hashrate, the more money a government entity would need to spend to perform a 51% attack.

So, the current cost of a 51% attack is pretty expensive but not outside the realm of possibility for a well funded entitiy such as large government. However, the future cost of a 51% attack is likely to be significantly higher. Will it be high enough to prevent a government from attempting it if/when they decide to try? We'll have to wait and see.