Kevrandrus
I knew Tobi couldn't be Madara though because his Sharingan is ALWAYS active as far as we've seen.
Therefore it had to have been taken from another [since Kakashi and Danzo couldn't shut theirs off either]
Itachi generally had his normal sharingan on all the time too. Once you become so good with the sharingan, I'd bet constant release is kind of like a form of training.
Danzo and Kakashi's sharingan were borrowed from other Uchiha, so the rules behind their activation differ. Since they have no control over turning it on or off, they remain always on, and the only way to stop them from pulling all the chakra from your body is to liberally cover them.
Furthermore, the rules are different for the Eternal Magenkyo. From what I know, the user won't go blind unless they really overexert their eyes. Sustaining Magenkyo doesn't seem to be an issue.
I suppose maybe Eternal Magenkyo could work sort of like taking an Uchiha's eyes, where they're forced on all the time... Seeing as they take the eyes of another Uchiha...
Considering that... My bet is on Izuna o-o...
He's the only person I can think of that's been introduced that could have the eyes. It would mean that everything we know about Madara's past is a lie, but it's not like that sort of thing is uncommon in manga/anime.
It would probably mean that Izuna's eyes weren't just passed over, but where instead taken by force maybe... Which would cause resentment towards Madara. What better way to get back at him than to take the eyes back, knock him off and replace his body with yours...
eh... I'm tired... and I think I'm rambling
sweatdrop
