With capslock on the password would be entered as 'aAaAaA' (which would pass) not 'AAAAAA' (which would fail). There is no guessing, it is just the inverse.

That's a very Windows-centric view. On OS X, caps lock + shift is still uppercased.

Facebook only accounts for accidental Windows caps lock, not OS X.

Accepting the entirely uppercased password would significantly reduce the number of unique passwords needed to guess a user's password.

Also, while caps lock + shift is still uppercased, caps lock has no effect on the non-alpha keys. Indeed on a Mac, caps-lock is not shift-lock, it's literally caps-lock: on my French layout, caps-lock'd & gives &, not 1. Since keys with diacritics and other marks like é è à ç adn ù are first-class keys on a french layout, they themselves are capitalized by caps-lock, and not giving in to the shift behavior (which would yield 2 7 0 9 and %). This allows to type É È À Ç and Ù without composition.

If you want the caps-lock-gives-numerics behavior you need to set your layout to "French — numerical" — its icon is a french flag with 123 at the bottom — instead of simply "French".

Wow, that strikes me as strange. Windows and Linux both shift to lowercase when capslock is on.

Does anyone know the behavior of other operating systems? Or is it an Apple-specific behavior?

Actually, a Linux-centric view. :) I thought Apple removed the caps lock key a long time ago...

Thats weird! I had always assumed that Shift+Caps Lock is lowercased in all OSes.