Quote from: cunicula on March 19, 2012, 04:49:51 AM

Because the mechanism against external attacks as you call them also works as a defense against internal attacks. Proof-of-work would be costly and redundant (read uselss).

You are complexly mixing up the different concepts of 'quantity of security' and 'quality of security'

If is like having a huge poorly trained army (that may be able to defend a country from external war)...
However you need special elite forces to defend against internal and sensitive disputes (such as dealing with spy's).

By your logic, because the special forces cannot defend an entire country against an invasion, they are:

Quote from: cunicula on March 19, 2012, 04:49:51 AM

Useless and costly -> completely discredited

Im arguing that more than one type of security is required. and for defending against internal attacks, the extremely high quality of the security that we have is a good thing.

The problem the proof-of-stake is that it requires TRUST. You must trust the people who have large numbers of bitcoin, to be both active, and not malicious with their investment. With the current proof-of-work being stakeholder counts for nill as you dont need defence, if you are not transacting your bitcoins.

A web-of-trust, (or even a proof-of-stake, a type of web-of-trust), that provides a lower grade of security, but at a much lower cost (so we can afford a very large quantity), is good for the 2nd line of defence, that we use against 51% attacks

However I do not agree that the proof-of-work is made irrelevant by the proof-of-stake idea. Rather I think that they provide solutions to different problems.