Quote from: aceat64 on August 16, 2010, 04:14:11 PM

1) The point of Bitcoin is to be a global currency, it doesn't make sense to use Bitcoin as a replacement for a national currency

You can say that, but it would be nice to use it on a smaller scale. It is interesting to think about how to achieve this without making the system too vulnerable.
Checkpoints could be one possibility. Maybe there are others.

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2) Block chain checkpoints are already done at each release of the client software
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A decentralized system does not have centralized upgrades, and there is no one program that everybody will use.
Do you envision a global currency with only one client program?
And where in the chain is the checkpoint placed exactly, and what node decides this.

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3) To generate a longer chain from scratch doesn't require more power (CPU time) then the network currently has, it requires more power then the network has put into the chain since the start. The current chain has had unbelievable amounts of CPU time go into generating it.

Of course time matters. But, you don't know how long the hidden part has been working. And if it has more power, it will eventually have done more work as well. But I agree, that for one giant global system, this might not be a big issue.

How would people react if some governments declared that they didn't like the system, and would now start an independent chain to make all current coins worthless. That in itself might create a panic, and destroy the system. With more recent checkpoints, the system would be less speculative.

Let me turn it around. With a global bitxoin system, what is a good reason that nodes can not freeze all blocks older than say 10 hours of accumulated difficulty. Where is the downside? Is it really considered a desired feature that a part of the network can be hidden for many hours and come back again with a long chain? Or is it just that checkpoints
haven't been implemented because the system is still so new?

Cheers.