I say, if you can get access to all private keys, by individually hacking every machine on the world, than you don't need a 51% attack or anything else. You already control the network.
But that doesn't have anything to do, with a weakness of the Bitcoin Network. Getting your twitter password stolen from your trojan infestested PC is also not a weakness of Twitter.
Correct. But if Twitter could guard against that, it would benefit from it.
So what I'm saying is that because of how Bitcoin works, it would be even easier for Bitcoin to guard against non-Bitcoin problems, than for Twitter - because Bitcoin can get those protections built into it much easier due to the nature of its community.
My gripe is with knowing that people have thought of this, a lot, but to day very few have published any of their research. Many have gone on to create alternate cryptocurrencies, rather than waste their time discussing their ideals with the Bitcoin community. Bitcoin has a lot going for it... So, if you come across something addressing this, or someone, motivate them to spend time on it, to study it, and to publish their research or insights where the community can have easy access to it...
So, you want a secure system where nobody needs any kind of password/private key? Good luck with that.
There are already tons of projects out there do create private keys far away from the internet.