> Enter it once on a compromised system and it's game over The same is true of any heavily used system today. All systems: banks, credit cards, facebook, etc.

> Enter it once on a compromised system and it's game over The same is true of any heavily used system today. All systems: banks, credit cards, facebook, etc. use "something you know". "Something you own" has just recently picked up steam in the form of two factor authentication, but then again, how many people you know actually use that? The only thing that I know of/heard of that might hold up against the type of attack that you describe is the behavioral keys: i.e. a key which is something about you that you dont necessarily know yourself, e.g. your style of chess, or your phrasing of sentences.