I've read so many different multi-factor authentication schemes, and they're often brilliant, but I've yet to come across one that would pass the "my grandpa co

I've read so many different multi-factor authentication schemes, and they're often brilliant, but I've yet to come across one that would pass the "my grandpa could use it" usability test. The holy grail for security, to me, will be something (an OS with it elegantly integrated for example) that the user has to try hard not to use, but doesn't feel like they're having an O'Reilly encryption book rammed down their gullet either.